1853 строки
71 KiB
Plaintext
1853 строки
71 KiB
Plaintext
Booting the Linux/ppc kernel without Open Firmware
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--------------------------------------------------
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(c) 2005 Benjamin Herrenschmidt <benh at kernel.crashing.org>,
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IBM Corp.
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(c) 2005 Becky Bruce <becky.bruce at freescale.com>,
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Freescale Semiconductor, FSL SOC and 32-bit additions
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(c) 2006 MontaVista Software, Inc.
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Flash chip node definition
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May 18, 2005: Rev 0.1 - Initial draft, no chapter III yet.
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May 19, 2005: Rev 0.2 - Add chapter III and bits & pieces here or
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clarifies the fact that a lot of things are
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optional, the kernel only requires a very
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small device tree, though it is encouraged
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to provide an as complete one as possible.
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May 24, 2005: Rev 0.3 - Precise that DT block has to be in RAM
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- Misc fixes
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- Define version 3 and new format version 16
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for the DT block (version 16 needs kernel
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patches, will be fwd separately).
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String block now has a size, and full path
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is replaced by unit name for more
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compactness.
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linux,phandle is made optional, only nodes
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that are referenced by other nodes need it.
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"name" property is now automatically
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deduced from the unit name
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June 1, 2005: Rev 0.4 - Correct confusion between OF_DT_END and
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OF_DT_END_NODE in structure definition.
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- Change version 16 format to always align
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property data to 4 bytes. Since tokens are
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already aligned, that means no specific
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required alignment between property size
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and property data. The old style variable
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alignment would make it impossible to do
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"simple" insertion of properties using
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memove (thanks Milton for
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noticing). Updated kernel patch as well
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- Correct a few more alignment constraints
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- Add a chapter about the device-tree
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compiler and the textural representation of
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the tree that can be "compiled" by dtc.
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November 21, 2005: Rev 0.5
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- Additions/generalizations for 32-bit
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- Changed to reflect the new arch/powerpc
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structure
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- Added chapter VI
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ToDo:
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- Add some definitions of interrupt tree (simple/complex)
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- Add some definitions for pci host bridges
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- Add some common address format examples
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- Add definitions for standard properties and "compatible"
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names for cells that are not already defined by the existing
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OF spec.
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- Compare FSL SOC use of PCI to standard and make sure no new
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node definition required.
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- Add more information about node definitions for SOC devices
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that currently have no standard, like the FSL CPM.
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I - Introduction
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================
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During the recent development of the Linux/ppc64 kernel, and more
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specifically, the addition of new platform types outside of the old
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IBM pSeries/iSeries pair, it was decided to enforce some strict rules
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regarding the kernel entry and bootloader <-> kernel interfaces, in
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order to avoid the degeneration that had become the ppc32 kernel entry
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point and the way a new platform should be added to the kernel. The
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legacy iSeries platform breaks those rules as it predates this scheme,
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but no new board support will be accepted in the main tree that
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doesn't follows them properly. In addition, since the advent of the
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arch/powerpc merged architecture for ppc32 and ppc64, new 32-bit
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platforms and 32-bit platforms which move into arch/powerpc will be
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required to use these rules as well.
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The main requirement that will be defined in more detail below is
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the presence of a device-tree whose format is defined after Open
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Firmware specification. However, in order to make life easier
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to embedded board vendors, the kernel doesn't require the device-tree
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to represent every device in the system and only requires some nodes
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and properties to be present. This will be described in detail in
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section III, but, for example, the kernel does not require you to
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create a node for every PCI device in the system. It is a requirement
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to have a node for PCI host bridges in order to provide interrupt
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routing informations and memory/IO ranges, among others. It is also
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recommended to define nodes for on chip devices and other busses that
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don't specifically fit in an existing OF specification. This creates a
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great flexibility in the way the kernel can then probe those and match
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drivers to device, without having to hard code all sorts of tables. It
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also makes it more flexible for board vendors to do minor hardware
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upgrades without significantly impacting the kernel code or cluttering
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it with special cases.
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1) Entry point for arch/powerpc
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-------------------------------
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There is one and one single entry point to the kernel, at the start
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of the kernel image. That entry point supports two calling
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conventions:
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a) Boot from Open Firmware. If your firmware is compatible
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with Open Firmware (IEEE 1275) or provides an OF compatible
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client interface API (support for "interpret" callback of
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forth words isn't required), you can enter the kernel with:
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r5 : OF callback pointer as defined by IEEE 1275
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bindings to powerpc. Only the 32 bit client interface
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is currently supported
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r3, r4 : address & length of an initrd if any or 0
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The MMU is either on or off; the kernel will run the
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trampoline located in arch/powerpc/kernel/prom_init.c to
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extract the device-tree and other information from open
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firmware and build a flattened device-tree as described
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in b). prom_init() will then re-enter the kernel using
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the second method. This trampoline code runs in the
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context of the firmware, which is supposed to handle all
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exceptions during that time.
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b) Direct entry with a flattened device-tree block. This entry
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point is called by a) after the OF trampoline and can also be
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called directly by a bootloader that does not support the Open
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Firmware client interface. It is also used by "kexec" to
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implement "hot" booting of a new kernel from a previous
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running one. This method is what I will describe in more
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details in this document, as method a) is simply standard Open
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Firmware, and thus should be implemented according to the
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various standard documents defining it and its binding to the
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PowerPC platform. The entry point definition then becomes:
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r3 : physical pointer to the device-tree block
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(defined in chapter II) in RAM
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r4 : physical pointer to the kernel itself. This is
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used by the assembly code to properly disable the MMU
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in case you are entering the kernel with MMU enabled
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and a non-1:1 mapping.
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r5 : NULL (as to differentiate with method a)
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Note about SMP entry: Either your firmware puts your other
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CPUs in some sleep loop or spin loop in ROM where you can get
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them out via a soft reset or some other means, in which case
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you don't need to care, or you'll have to enter the kernel
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with all CPUs. The way to do that with method b) will be
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described in a later revision of this document.
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2) Board support
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----------------
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64-bit kernels:
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Board supports (platforms) are not exclusive config options. An
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arbitrary set of board supports can be built in a single kernel
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image. The kernel will "know" what set of functions to use for a
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given platform based on the content of the device-tree. Thus, you
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should:
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a) add your platform support as a _boolean_ option in
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arch/powerpc/Kconfig, following the example of PPC_PSERIES,
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PPC_PMAC and PPC_MAPLE. The later is probably a good
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example of a board support to start from.
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b) create your main platform file as
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"arch/powerpc/platforms/myplatform/myboard_setup.c" and add it
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to the Makefile under the condition of your CONFIG_
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option. This file will define a structure of type "ppc_md"
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containing the various callbacks that the generic code will
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use to get to your platform specific code
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c) Add a reference to your "ppc_md" structure in the
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"machines" table in arch/powerpc/kernel/setup_64.c if you are
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a 64-bit platform.
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d) request and get assigned a platform number (see PLATFORM_*
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constants in include/asm-powerpc/processor.h
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32-bit embedded kernels:
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Currently, board support is essentially an exclusive config option.
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The kernel is configured for a single platform. Part of the reason
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for this is to keep kernels on embedded systems small and efficient;
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part of this is due to the fact the code is already that way. In the
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future, a kernel may support multiple platforms, but only if the
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platforms feature the same core architectire. A single kernel build
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cannot support both configurations with Book E and configurations
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with classic Powerpc architectures.
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32-bit embedded platforms that are moved into arch/powerpc using a
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flattened device tree should adopt the merged tree practice of
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setting ppc_md up dynamically, even though the kernel is currently
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built with support for only a single platform at a time. This allows
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unification of the setup code, and will make it easier to go to a
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multiple-platform-support model in the future.
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NOTE: I believe the above will be true once Ben's done with the merge
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of the boot sequences.... someone speak up if this is wrong!
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To add a 32-bit embedded platform support, follow the instructions
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for 64-bit platforms above, with the exception that the Kconfig
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option should be set up such that the kernel builds exclusively for
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the platform selected. The processor type for the platform should
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enable another config option to select the specific board
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supported.
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NOTE: If ben doesn't merge the setup files, may need to change this to
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point to setup_32.c
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I will describe later the boot process and various callbacks that
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your platform should implement.
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II - The DT block format
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========================
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This chapter defines the actual format of the flattened device-tree
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passed to the kernel. The actual content of it and kernel requirements
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are described later. You can find example of code manipulating that
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format in various places, including arch/powerpc/kernel/prom_init.c
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which will generate a flattened device-tree from the Open Firmware
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representation, or the fs2dt utility which is part of the kexec tools
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which will generate one from a filesystem representation. It is
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expected that a bootloader like uboot provides a bit more support,
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that will be discussed later as well.
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Note: The block has to be in main memory. It has to be accessible in
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both real mode and virtual mode with no mapping other than main
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memory. If you are writing a simple flash bootloader, it should copy
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the block to RAM before passing it to the kernel.
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1) Header
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---------
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The kernel is entered with r3 pointing to an area of memory that is
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roughly described in include/asm-powerpc/prom.h by the structure
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boot_param_header:
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struct boot_param_header {
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u32 magic; /* magic word OF_DT_HEADER */
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u32 totalsize; /* total size of DT block */
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u32 off_dt_struct; /* offset to structure */
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u32 off_dt_strings; /* offset to strings */
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u32 off_mem_rsvmap; /* offset to memory reserve map
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*/
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u32 version; /* format version */
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u32 last_comp_version; /* last compatible version */
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/* version 2 fields below */
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u32 boot_cpuid_phys; /* Which physical CPU id we're
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booting on */
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/* version 3 fields below */
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u32 size_dt_strings; /* size of the strings block */
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};
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Along with the constants:
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/* Definitions used by the flattened device tree */
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#define OF_DT_HEADER 0xd00dfeed /* 4: version,
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4: total size */
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#define OF_DT_BEGIN_NODE 0x1 /* Start node: full name
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*/
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#define OF_DT_END_NODE 0x2 /* End node */
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#define OF_DT_PROP 0x3 /* Property: name off,
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size, content */
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#define OF_DT_END 0x9
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All values in this header are in big endian format, the various
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fields in this header are defined more precisely below. All
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"offset" values are in bytes from the start of the header; that is
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from the value of r3.
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- magic
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This is a magic value that "marks" the beginning of the
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device-tree block header. It contains the value 0xd00dfeed and is
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defined by the constant OF_DT_HEADER
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- totalsize
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This is the total size of the DT block including the header. The
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"DT" block should enclose all data structures defined in this
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chapter (who are pointed to by offsets in this header). That is,
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the device-tree structure, strings, and the memory reserve map.
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- off_dt_struct
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This is an offset from the beginning of the header to the start
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of the "structure" part the device tree. (see 2) device tree)
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- off_dt_strings
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This is an offset from the beginning of the header to the start
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of the "strings" part of the device-tree
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- off_mem_rsvmap
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This is an offset from the beginning of the header to the start
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of the reserved memory map. This map is a list of pairs of 64
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bit integers. Each pair is a physical address and a size. The
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list is terminated by an entry of size 0. This map provides the
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kernel with a list of physical memory areas that are "reserved"
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and thus not to be used for memory allocations, especially during
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early initialization. The kernel needs to allocate memory during
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boot for things like un-flattening the device-tree, allocating an
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MMU hash table, etc... Those allocations must be done in such a
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way to avoid overriding critical things like, on Open Firmware
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capable machines, the RTAS instance, or on some pSeries, the TCE
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tables used for the iommu. Typically, the reserve map should
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contain _at least_ this DT block itself (header,total_size). If
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you are passing an initrd to the kernel, you should reserve it as
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well. You do not need to reserve the kernel image itself. The map
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should be 64 bit aligned.
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- version
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This is the version of this structure. Version 1 stops
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here. Version 2 adds an additional field boot_cpuid_phys.
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Version 3 adds the size of the strings block, allowing the kernel
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to reallocate it easily at boot and free up the unused flattened
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structure after expansion. Version 16 introduces a new more
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"compact" format for the tree itself that is however not backward
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compatible. You should always generate a structure of the highest
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version defined at the time of your implementation. Currently
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that is version 16, unless you explicitly aim at being backward
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compatible.
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- last_comp_version
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Last compatible version. This indicates down to what version of
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the DT block you are backward compatible. For example, version 2
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is backward compatible with version 1 (that is, a kernel build
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for version 1 will be able to boot with a version 2 format). You
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should put a 1 in this field if you generate a device tree of
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version 1 to 3, or 0x10 if you generate a tree of version 0x10
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using the new unit name format.
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- boot_cpuid_phys
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This field only exist on version 2 headers. It indicate which
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physical CPU ID is calling the kernel entry point. This is used,
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among others, by kexec. If you are on an SMP system, this value
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should match the content of the "reg" property of the CPU node in
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the device-tree corresponding to the CPU calling the kernel entry
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point (see further chapters for more informations on the required
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device-tree contents)
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So the typical layout of a DT block (though the various parts don't
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need to be in that order) looks like this (addresses go from top to
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bottom):
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------------------------------
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r3 -> | struct boot_param_header |
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------------------------------
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| (alignment gap) (*) |
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------------------------------
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| memory reserve map |
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------------------------------
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| (alignment gap) |
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------------------------------
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| device-tree structure |
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------------------------------
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| (alignment gap) |
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------------------------------
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| device-tree strings |
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-----> ------------------------------
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--- (r3 + totalsize)
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(*) The alignment gaps are not necessarily present; their presence
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and size are dependent on the various alignment requirements of
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the individual data blocks.
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2) Device tree generalities
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---------------------------
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This device-tree itself is separated in two different blocks, a
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structure block and a strings block. Both need to be aligned to a 4
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byte boundary.
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First, let's quickly describe the device-tree concept before detailing
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the storage format. This chapter does _not_ describe the detail of the
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required types of nodes & properties for the kernel, this is done
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later in chapter III.
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The device-tree layout is strongly inherited from the definition of
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the Open Firmware IEEE 1275 device-tree. It's basically a tree of
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nodes, each node having two or more named properties. A property can
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have a value or not.
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It is a tree, so each node has one and only one parent except for the
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root node who has no parent.
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A node has 2 names. The actual node name is generally contained in a
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property of type "name" in the node property list whose value is a
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zero terminated string and is mandatory for version 1 to 3 of the
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format definition (as it is in Open Firmware). Version 0x10 makes it
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optional as it can generate it from the unit name defined below.
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There is also a "unit name" that is used to differentiate nodes with
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the same name at the same level, it is usually made of the node
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names, the "@" sign, and a "unit address", which definition is
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specific to the bus type the node sits on.
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The unit name doesn't exist as a property per-se but is included in
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the device-tree structure. It is typically used to represent "path" in
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the device-tree. More details about the actual format of these will be
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below.
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The kernel powerpc generic code does not make any formal use of the
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unit address (though some board support code may do) so the only real
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requirement here for the unit address is to ensure uniqueness of
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the node unit name at a given level of the tree. Nodes with no notion
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of address and no possible sibling of the same name (like /memory or
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/cpus) may omit the unit address in the context of this specification,
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or use the "@0" default unit address. The unit name is used to define
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a node "full path", which is the concatenation of all parent node
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unit names separated with "/".
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The root node doesn't have a defined name, and isn't required to have
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a name property either if you are using version 3 or earlier of the
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format. It also has no unit address (no @ symbol followed by a unit
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address). The root node unit name is thus an empty string. The full
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path to the root node is "/".
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Every node which actually represents an actual device (that is, a node
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which isn't only a virtual "container" for more nodes, like "/cpus"
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is) is also required to have a "device_type" property indicating the
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type of node .
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Finally, every node that can be referenced from a property in another
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node is required to have a "linux,phandle" property. Real open
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firmware implementations provide a unique "phandle" value for every
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node that the "prom_init()" trampoline code turns into
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"linux,phandle" properties. However, this is made optional if the
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flattened device tree is used directly. An example of a node
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referencing another node via "phandle" is when laying out the
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interrupt tree which will be described in a further version of this
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document.
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This "linux, phandle" property is a 32 bit value that uniquely
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identifies a node. You are free to use whatever values or system of
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values, internal pointers, or whatever to generate these, the only
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requirement is that every node for which you provide that property has
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a unique value for it.
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Here is an example of a simple device-tree. In this example, an "o"
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designates a node followed by the node unit name. Properties are
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presented with their name followed by their content. "content"
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represents an ASCII string (zero terminated) value, while <content>
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represents a 32 bit hexadecimal value. The various nodes in this
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example will be discussed in a later chapter. At this point, it is
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only meant to give you a idea of what a device-tree looks like. I have
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purposefully kept the "name" and "linux,phandle" properties which
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aren't necessary in order to give you a better idea of what the tree
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looks like in practice.
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/ o device-tree
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|- name = "device-tree"
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|- model = "MyBoardName"
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|- compatible = "MyBoardFamilyName"
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|- #address-cells = <2>
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|- #size-cells = <2>
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|- linux,phandle = <0>
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o cpus
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| | - name = "cpus"
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| | - linux,phandle = <1>
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| | - #address-cells = <1>
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|
| | - #size-cells = <0>
|
|
| |
|
|
| o PowerPC,970@0
|
|
| |- name = "PowerPC,970"
|
|
| |- device_type = "cpu"
|
|
| |- reg = <0>
|
|
| |- clock-frequency = <5f5e1000>
|
|
| |- 64-bit
|
|
| |- linux,phandle = <2>
|
|
|
|
|
o memory@0
|
|
| |- name = "memory"
|
|
| |- device_type = "memory"
|
|
| |- reg = <00000000 00000000 00000000 20000000>
|
|
| |- linux,phandle = <3>
|
|
|
|
|
o chosen
|
|
|- name = "chosen"
|
|
|- bootargs = "root=/dev/sda2"
|
|
|- linux,phandle = <4>
|
|
|
|
This tree is almost a minimal tree. It pretty much contains the
|
|
minimal set of required nodes and properties to boot a linux kernel;
|
|
that is, some basic model informations at the root, the CPUs, and the
|
|
physical memory layout. It also includes misc information passed
|
|
through /chosen, like in this example, the platform type (mandatory)
|
|
and the kernel command line arguments (optional).
|
|
|
|
The /cpus/PowerPC,970@0/64-bit property is an example of a
|
|
property without a value. All other properties have a value. The
|
|
significance of the #address-cells and #size-cells properties will be
|
|
explained in chapter IV which defines precisely the required nodes and
|
|
properties and their content.
|
|
|
|
|
|
3) Device tree "structure" block
|
|
|
|
The structure of the device tree is a linearized tree structure. The
|
|
"OF_DT_BEGIN_NODE" token starts a new node, and the "OF_DT_END_NODE"
|
|
ends that node definition. Child nodes are simply defined before
|
|
"OF_DT_END_NODE" (that is nodes within the node). A 'token' is a 32
|
|
bit value. The tree has to be "finished" with a OF_DT_END token
|
|
|
|
Here's the basic structure of a single node:
|
|
|
|
* token OF_DT_BEGIN_NODE (that is 0x00000001)
|
|
* for version 1 to 3, this is the node full path as a zero
|
|
terminated string, starting with "/". For version 16 and later,
|
|
this is the node unit name only (or an empty string for the
|
|
root node)
|
|
* [align gap to next 4 bytes boundary]
|
|
* for each property:
|
|
* token OF_DT_PROP (that is 0x00000003)
|
|
* 32 bit value of property value size in bytes (or 0 of no
|
|
* value)
|
|
* 32 bit value of offset in string block of property name
|
|
* property value data if any
|
|
* [align gap to next 4 bytes boundary]
|
|
* [child nodes if any]
|
|
* token OF_DT_END_NODE (that is 0x00000002)
|
|
|
|
So the node content can be summarised as a start token, a full path,
|
|
a list of properties, a list of child nodes, and an end token. Every
|
|
child node is a full node structure itself as defined above.
|
|
|
|
4) Device tree "strings" block
|
|
|
|
In order to save space, property names, which are generally redundant,
|
|
are stored separately in the "strings" block. This block is simply the
|
|
whole bunch of zero terminated strings for all property names
|
|
concatenated together. The device-tree property definitions in the
|
|
structure block will contain offset values from the beginning of the
|
|
strings block.
|
|
|
|
|
|
III - Required content of the device tree
|
|
=========================================
|
|
|
|
WARNING: All "linux,*" properties defined in this document apply only
|
|
to a flattened device-tree. If your platform uses a real
|
|
implementation of Open Firmware or an implementation compatible with
|
|
the Open Firmware client interface, those properties will be created
|
|
by the trampoline code in the kernel's prom_init() file. For example,
|
|
that's where you'll have to add code to detect your board model and
|
|
set the platform number. However, when using the flattened device-tree
|
|
entry point, there is no prom_init() pass, and thus you have to
|
|
provide those properties yourself.
|
|
|
|
|
|
1) Note about cells and address representation
|
|
----------------------------------------------
|
|
|
|
The general rule is documented in the various Open Firmware
|
|
documentations. If you chose to describe a bus with the device-tree
|
|
and there exist an OF bus binding, then you should follow the
|
|
specification. However, the kernel does not require every single
|
|
device or bus to be described by the device tree.
|
|
|
|
In general, the format of an address for a device is defined by the
|
|
parent bus type, based on the #address-cells and #size-cells
|
|
property. In the absence of such a property, the parent's parent
|
|
values are used, etc... The kernel requires the root node to have
|
|
those properties defining addresses format for devices directly mapped
|
|
on the processor bus.
|
|
|
|
Those 2 properties define 'cells' for representing an address and a
|
|
size. A "cell" is a 32 bit number. For example, if both contain 2
|
|
like the example tree given above, then an address and a size are both
|
|
composed of 2 cells, and each is a 64 bit number (cells are
|
|
concatenated and expected to be in big endian format). Another example
|
|
is the way Apple firmware defines them, with 2 cells for an address
|
|
and one cell for a size. Most 32-bit implementations should define
|
|
#address-cells and #size-cells to 1, which represents a 32-bit value.
|
|
Some 32-bit processors allow for physical addresses greater than 32
|
|
bits; these processors should define #address-cells as 2.
|
|
|
|
"reg" properties are always a tuple of the type "address size" where
|
|
the number of cells of address and size is specified by the bus
|
|
#address-cells and #size-cells. When a bus supports various address
|
|
spaces and other flags relative to a given address allocation (like
|
|
prefetchable, etc...) those flags are usually added to the top level
|
|
bits of the physical address. For example, a PCI physical address is
|
|
made of 3 cells, the bottom two containing the actual address itself
|
|
while the top cell contains address space indication, flags, and pci
|
|
bus & device numbers.
|
|
|
|
For busses that support dynamic allocation, it's the accepted practice
|
|
to then not provide the address in "reg" (keep it 0) though while
|
|
providing a flag indicating the address is dynamically allocated, and
|
|
then, to provide a separate "assigned-addresses" property that
|
|
contains the fully allocated addresses. See the PCI OF bindings for
|
|
details.
|
|
|
|
In general, a simple bus with no address space bits and no dynamic
|
|
allocation is preferred if it reflects your hardware, as the existing
|
|
kernel address parsing functions will work out of the box. If you
|
|
define a bus type with a more complex address format, including things
|
|
like address space bits, you'll have to add a bus translator to the
|
|
prom_parse.c file of the recent kernels for your bus type.
|
|
|
|
The "reg" property only defines addresses and sizes (if #size-cells
|
|
is non-0) within a given bus. In order to translate addresses upward
|
|
(that is into parent bus addresses, and possibly into cpu physical
|
|
addresses), all busses must contain a "ranges" property. If the
|
|
"ranges" property is missing at a given level, it's assumed that
|
|
translation isn't possible. The format of the "ranges" property for a
|
|
bus is a list of:
|
|
|
|
bus address, parent bus address, size
|
|
|
|
"bus address" is in the format of the bus this bus node is defining,
|
|
that is, for a PCI bridge, it would be a PCI address. Thus, (bus
|
|
address, size) defines a range of addresses for child devices. "parent
|
|
bus address" is in the format of the parent bus of this bus. For
|
|
example, for a PCI host controller, that would be a CPU address. For a
|
|
PCI<->ISA bridge, that would be a PCI address. It defines the base
|
|
address in the parent bus where the beginning of that range is mapped.
|
|
|
|
For a new 64 bit powerpc board, I recommend either the 2/2 format or
|
|
Apple's 2/1 format which is slightly more compact since sizes usually
|
|
fit in a single 32 bit word. New 32 bit powerpc boards should use a
|
|
1/1 format, unless the processor supports physical addresses greater
|
|
than 32-bits, in which case a 2/1 format is recommended.
|
|
|
|
|
|
2) Note about "compatible" properties
|
|
-------------------------------------
|
|
|
|
These properties are optional, but recommended in devices and the root
|
|
node. The format of a "compatible" property is a list of concatenated
|
|
zero terminated strings. They allow a device to express its
|
|
compatibility with a family of similar devices, in some cases,
|
|
allowing a single driver to match against several devices regardless
|
|
of their actual names.
|
|
|
|
3) Note about "name" properties
|
|
-------------------------------
|
|
|
|
While earlier users of Open Firmware like OldWorld macintoshes tended
|
|
to use the actual device name for the "name" property, it's nowadays
|
|
considered a good practice to use a name that is closer to the device
|
|
class (often equal to device_type). For example, nowadays, ethernet
|
|
controllers are named "ethernet", an additional "model" property
|
|
defining precisely the chip type/model, and "compatible" property
|
|
defining the family in case a single driver can driver more than one
|
|
of these chips. However, the kernel doesn't generally put any
|
|
restriction on the "name" property; it is simply considered good
|
|
practice to follow the standard and its evolutions as closely as
|
|
possible.
|
|
|
|
Note also that the new format version 16 makes the "name" property
|
|
optional. If it's absent for a node, then the node's unit name is then
|
|
used to reconstruct the name. That is, the part of the unit name
|
|
before the "@" sign is used (or the entire unit name if no "@" sign
|
|
is present).
|
|
|
|
4) Note about node and property names and character set
|
|
-------------------------------------------------------
|
|
|
|
While open firmware provides more flexible usage of 8859-1, this
|
|
specification enforces more strict rules. Nodes and properties should
|
|
be comprised only of ASCII characters 'a' to 'z', '0' to
|
|
'9', ',', '.', '_', '+', '#', '?', and '-'. Node names additionally
|
|
allow uppercase characters 'A' to 'Z' (property names should be
|
|
lowercase. The fact that vendors like Apple don't respect this rule is
|
|
irrelevant here). Additionally, node and property names should always
|
|
begin with a character in the range 'a' to 'z' (or 'A' to 'Z' for node
|
|
names).
|
|
|
|
The maximum number of characters for both nodes and property names
|
|
is 31. In the case of node names, this is only the leftmost part of
|
|
a unit name (the pure "name" property), it doesn't include the unit
|
|
address which can extend beyond that limit.
|
|
|
|
|
|
5) Required nodes and properties
|
|
--------------------------------
|
|
These are all that are currently required. However, it is strongly
|
|
recommended that you expose PCI host bridges as documented in the
|
|
PCI binding to open firmware, and your interrupt tree as documented
|
|
in OF interrupt tree specification.
|
|
|
|
a) The root node
|
|
|
|
The root node requires some properties to be present:
|
|
|
|
- model : this is your board name/model
|
|
- #address-cells : address representation for "root" devices
|
|
- #size-cells: the size representation for "root" devices
|
|
- device_type : This property shouldn't be necessary. However, if
|
|
you decide to create a device_type for your root node, make sure it
|
|
is _not_ "chrp" unless your platform is a pSeries or PAPR compliant
|
|
one for 64-bit, or a CHRP-type machine for 32-bit as this will
|
|
matched by the kernel this way.
|
|
|
|
Additionally, some recommended properties are:
|
|
|
|
- compatible : the board "family" generally finds its way here,
|
|
for example, if you have 2 board models with a similar layout,
|
|
that typically get driven by the same platform code in the
|
|
kernel, you would use a different "model" property but put a
|
|
value in "compatible". The kernel doesn't directly use that
|
|
value but it is generally useful.
|
|
|
|
The root node is also generally where you add additional properties
|
|
specific to your board like the serial number if any, that sort of
|
|
thing. It is recommended that if you add any "custom" property whose
|
|
name may clash with standard defined ones, you prefix them with your
|
|
vendor name and a comma.
|
|
|
|
b) The /cpus node
|
|
|
|
This node is the parent of all individual CPU nodes. It doesn't
|
|
have any specific requirements, though it's generally good practice
|
|
to have at least:
|
|
|
|
#address-cells = <00000001>
|
|
#size-cells = <00000000>
|
|
|
|
This defines that the "address" for a CPU is a single cell, and has
|
|
no meaningful size. This is not necessary but the kernel will assume
|
|
that format when reading the "reg" properties of a CPU node, see
|
|
below
|
|
|
|
c) The /cpus/* nodes
|
|
|
|
So under /cpus, you are supposed to create a node for every CPU on
|
|
the machine. There is no specific restriction on the name of the
|
|
CPU, though It's common practice to call it PowerPC,<name>. For
|
|
example, Apple uses PowerPC,G5 while IBM uses PowerPC,970FX.
|
|
|
|
Required properties:
|
|
|
|
- device_type : has to be "cpu"
|
|
- reg : This is the physical cpu number, it's a single 32 bit cell
|
|
and is also used as-is as the unit number for constructing the
|
|
unit name in the full path. For example, with 2 CPUs, you would
|
|
have the full path:
|
|
/cpus/PowerPC,970FX@0
|
|
/cpus/PowerPC,970FX@1
|
|
(unit addresses do not require leading zeroes)
|
|
- d-cache-line-size : one cell, L1 data cache line size in bytes
|
|
- i-cache-line-size : one cell, L1 instruction cache line size in
|
|
bytes
|
|
- d-cache-size : one cell, size of L1 data cache in bytes
|
|
- i-cache-size : one cell, size of L1 instruction cache in bytes
|
|
|
|
Recommended properties:
|
|
|
|
- timebase-frequency : a cell indicating the frequency of the
|
|
timebase in Hz. This is not directly used by the generic code,
|
|
but you are welcome to copy/paste the pSeries code for setting
|
|
the kernel timebase/decrementer calibration based on this
|
|
value.
|
|
- clock-frequency : a cell indicating the CPU core clock frequency
|
|
in Hz. A new property will be defined for 64 bit values, but if
|
|
your frequency is < 4Ghz, one cell is enough. Here as well as
|
|
for the above, the common code doesn't use that property, but
|
|
you are welcome to re-use the pSeries or Maple one. A future
|
|
kernel version might provide a common function for this.
|
|
|
|
You are welcome to add any property you find relevant to your board,
|
|
like some information about the mechanism used to soft-reset the
|
|
CPUs. For example, Apple puts the GPIO number for CPU soft reset
|
|
lines in there as a "soft-reset" property since they start secondary
|
|
CPUs by soft-resetting them.
|
|
|
|
|
|
d) the /memory node(s)
|
|
|
|
To define the physical memory layout of your board, you should
|
|
create one or more memory node(s). You can either create a single
|
|
node with all memory ranges in its reg property, or you can create
|
|
several nodes, as you wish. The unit address (@ part) used for the
|
|
full path is the address of the first range of memory defined by a
|
|
given node. If you use a single memory node, this will typically be
|
|
@0.
|
|
|
|
Required properties:
|
|
|
|
- device_type : has to be "memory"
|
|
- reg : This property contains all the physical memory ranges of
|
|
your board. It's a list of addresses/sizes concatenated
|
|
together, with the number of cells of each defined by the
|
|
#address-cells and #size-cells of the root node. For example,
|
|
with both of these properties being 2 like in the example given
|
|
earlier, a 970 based machine with 6Gb of RAM could typically
|
|
have a "reg" property here that looks like:
|
|
|
|
00000000 00000000 00000000 80000000
|
|
00000001 00000000 00000001 00000000
|
|
|
|
That is a range starting at 0 of 0x80000000 bytes and a range
|
|
starting at 0x100000000 and of 0x100000000 bytes. You can see
|
|
that there is no memory covering the IO hole between 2Gb and
|
|
4Gb. Some vendors prefer splitting those ranges into smaller
|
|
segments, but the kernel doesn't care.
|
|
|
|
e) The /chosen node
|
|
|
|
This node is a bit "special". Normally, that's where open firmware
|
|
puts some variable environment information, like the arguments, or
|
|
phandle pointers to nodes like the main interrupt controller, or the
|
|
default input/output devices.
|
|
|
|
This specification makes a few of these mandatory, but also defines
|
|
some linux-specific properties that would be normally constructed by
|
|
the prom_init() trampoline when booting with an OF client interface,
|
|
but that you have to provide yourself when using the flattened format.
|
|
|
|
Recommended properties:
|
|
|
|
- bootargs : This zero-terminated string is passed as the kernel
|
|
command line
|
|
- linux,stdout-path : This is the full path to your standard
|
|
console device if any. Typically, if you have serial devices on
|
|
your board, you may want to put the full path to the one set as
|
|
the default console in the firmware here, for the kernel to pick
|
|
it up as its own default console. If you look at the function
|
|
set_preferred_console() in arch/ppc64/kernel/setup.c, you'll see
|
|
that the kernel tries to find out the default console and has
|
|
knowledge of various types like 8250 serial ports. You may want
|
|
to extend this function to add your own.
|
|
- interrupt-controller : This is one cell containing a phandle
|
|
value that matches the "linux,phandle" property of your main
|
|
interrupt controller node. May be used for interrupt routing.
|
|
|
|
|
|
Note that u-boot creates and fills in the chosen node for platforms
|
|
that use it.
|
|
|
|
f) the /soc<SOCname> node
|
|
|
|
This node is used to represent a system-on-a-chip (SOC) and must be
|
|
present if the processor is a SOC. The top-level soc node contains
|
|
information that is global to all devices on the SOC. The node name
|
|
should contain a unit address for the SOC, which is the base address
|
|
of the memory-mapped register set for the SOC. The name of an soc
|
|
node should start with "soc", and the remainder of the name should
|
|
represent the part number for the soc. For example, the MPC8540's
|
|
soc node would be called "soc8540".
|
|
|
|
Required properties:
|
|
|
|
- device_type : Should be "soc"
|
|
- ranges : Should be defined as specified in 1) to describe the
|
|
translation of SOC addresses for memory mapped SOC registers.
|
|
- bus-frequency: Contains the bus frequency for the SOC node.
|
|
Typically, the value of this field is filled in by the boot
|
|
loader.
|
|
|
|
|
|
Recommended properties:
|
|
|
|
- reg : This property defines the address and size of the
|
|
memory-mapped registers that are used for the SOC node itself.
|
|
It does not include the child device registers - these will be
|
|
defined inside each child node. The address specified in the
|
|
"reg" property should match the unit address of the SOC node.
|
|
- #address-cells : Address representation for "soc" devices. The
|
|
format of this field may vary depending on whether or not the
|
|
device registers are memory mapped. For memory mapped
|
|
registers, this field represents the number of cells needed to
|
|
represent the address of the registers. For SOCs that do not
|
|
use MMIO, a special address format should be defined that
|
|
contains enough cells to represent the required information.
|
|
See 1) above for more details on defining #address-cells.
|
|
- #size-cells : Size representation for "soc" devices
|
|
- #interrupt-cells : Defines the width of cells used to represent
|
|
interrupts. Typically this value is <2>, which includes a
|
|
32-bit number that represents the interrupt number, and a
|
|
32-bit number that represents the interrupt sense and level.
|
|
This field is only needed if the SOC contains an interrupt
|
|
controller.
|
|
|
|
The SOC node may contain child nodes for each SOC device that the
|
|
platform uses. Nodes should not be created for devices which exist
|
|
on the SOC but are not used by a particular platform. See chapter VI
|
|
for more information on how to specify devices that are part of an
|
|
SOC.
|
|
|
|
Example SOC node for the MPC8540:
|
|
|
|
soc8540@e0000000 {
|
|
#address-cells = <1>;
|
|
#size-cells = <1>;
|
|
#interrupt-cells = <2>;
|
|
device_type = "soc";
|
|
ranges = <00000000 e0000000 00100000>
|
|
reg = <e0000000 00003000>;
|
|
bus-frequency = <0>;
|
|
}
|
|
|
|
|
|
|
|
IV - "dtc", the device tree compiler
|
|
====================================
|
|
|
|
|
|
dtc source code can be found at
|
|
<http://ozlabs.org/~dgibson/dtc/dtc.tar.gz>
|
|
|
|
WARNING: This version is still in early development stage; the
|
|
resulting device-tree "blobs" have not yet been validated with the
|
|
kernel. The current generated bloc lacks a useful reserve map (it will
|
|
be fixed to generate an empty one, it's up to the bootloader to fill
|
|
it up) among others. The error handling needs work, bugs are lurking,
|
|
etc...
|
|
|
|
dtc basically takes a device-tree in a given format and outputs a
|
|
device-tree in another format. The currently supported formats are:
|
|
|
|
Input formats:
|
|
-------------
|
|
|
|
- "dtb": "blob" format, that is a flattened device-tree block
|
|
with
|
|
header all in a binary blob.
|
|
- "dts": "source" format. This is a text file containing a
|
|
"source" for a device-tree. The format is defined later in this
|
|
chapter.
|
|
- "fs" format. This is a representation equivalent to the
|
|
output of /proc/device-tree, that is nodes are directories and
|
|
properties are files
|
|
|
|
Output formats:
|
|
---------------
|
|
|
|
- "dtb": "blob" format
|
|
- "dts": "source" format
|
|
- "asm": assembly language file. This is a file that can be
|
|
sourced by gas to generate a device-tree "blob". That file can
|
|
then simply be added to your Makefile. Additionally, the
|
|
assembly file exports some symbols that can be used.
|
|
|
|
|
|
The syntax of the dtc tool is
|
|
|
|
dtc [-I <input-format>] [-O <output-format>]
|
|
[-o output-filename] [-V output_version] input_filename
|
|
|
|
|
|
The "output_version" defines what versio of the "blob" format will be
|
|
generated. Supported versions are 1,2,3 and 16. The default is
|
|
currently version 3 but that may change in the future to version 16.
|
|
|
|
Additionally, dtc performs various sanity checks on the tree, like the
|
|
uniqueness of linux, phandle properties, validity of strings, etc...
|
|
|
|
The format of the .dts "source" file is "C" like, supports C and C++
|
|
style comments.
|
|
|
|
/ {
|
|
}
|
|
|
|
The above is the "device-tree" definition. It's the only statement
|
|
supported currently at the toplevel.
|
|
|
|
/ {
|
|
property1 = "string_value"; /* define a property containing a 0
|
|
* terminated string
|
|
*/
|
|
|
|
property2 = <1234abcd>; /* define a property containing a
|
|
* numerical 32 bits value (hexadecimal)
|
|
*/
|
|
|
|
property3 = <12345678 12345678 deadbeef>;
|
|
/* define a property containing 3
|
|
* numerical 32 bits values (cells) in
|
|
* hexadecimal
|
|
*/
|
|
property4 = [0a 0b 0c 0d de ea ad be ef];
|
|
/* define a property whose content is
|
|
* an arbitrary array of bytes
|
|
*/
|
|
|
|
childnode@addresss { /* define a child node named "childnode"
|
|
* whose unit name is "childnode at
|
|
* address"
|
|
*/
|
|
|
|
childprop = "hello\n"; /* define a property "childprop" of
|
|
* childnode (in this case, a string)
|
|
*/
|
|
};
|
|
};
|
|
|
|
Nodes can contain other nodes etc... thus defining the hierarchical
|
|
structure of the tree.
|
|
|
|
Strings support common escape sequences from C: "\n", "\t", "\r",
|
|
"\(octal value)", "\x(hex value)".
|
|
|
|
It is also suggested that you pipe your source file through cpp (gcc
|
|
preprocessor) so you can use #include's, #define for constants, etc...
|
|
|
|
Finally, various options are planned but not yet implemented, like
|
|
automatic generation of phandles, labels (exported to the asm file so
|
|
you can point to a property content and change it easily from whatever
|
|
you link the device-tree with), label or path instead of numeric value
|
|
in some cells to "point" to a node (replaced by a phandle at compile
|
|
time), export of reserve map address to the asm file, ability to
|
|
specify reserve map content at compile time, etc...
|
|
|
|
We may provide a .h include file with common definitions of that
|
|
proves useful for some properties (like building PCI properties or
|
|
interrupt maps) though it may be better to add a notion of struct
|
|
definitions to the compiler...
|
|
|
|
|
|
V - Recommendations for a bootloader
|
|
====================================
|
|
|
|
|
|
Here are some various ideas/recommendations that have been proposed
|
|
while all this has been defined and implemented.
|
|
|
|
- The bootloader may want to be able to use the device-tree itself
|
|
and may want to manipulate it (to add/edit some properties,
|
|
like physical memory size or kernel arguments). At this point, 2
|
|
choices can be made. Either the bootloader works directly on the
|
|
flattened format, or the bootloader has its own internal tree
|
|
representation with pointers (similar to the kernel one) and
|
|
re-flattens the tree when booting the kernel. The former is a bit
|
|
more difficult to edit/modify, the later requires probably a bit
|
|
more code to handle the tree structure. Note that the structure
|
|
format has been designed so it's relatively easy to "insert"
|
|
properties or nodes or delete them by just memmoving things
|
|
around. It contains no internal offsets or pointers for this
|
|
purpose.
|
|
|
|
- An example of code for iterating nodes & retrieving properties
|
|
directly from the flattened tree format can be found in the kernel
|
|
file arch/ppc64/kernel/prom.c, look at scan_flat_dt() function,
|
|
its usage in early_init_devtree(), and the corresponding various
|
|
early_init_dt_scan_*() callbacks. That code can be re-used in a
|
|
GPL bootloader, and as the author of that code, I would be happy
|
|
to discuss possible free licencing to any vendor who wishes to
|
|
integrate all or part of this code into a non-GPL bootloader.
|
|
|
|
|
|
|
|
VI - System-on-a-chip devices and nodes
|
|
=======================================
|
|
|
|
Many companies are now starting to develop system-on-a-chip
|
|
processors, where the processor core (cpu) and many peripheral devices
|
|
exist on a single piece of silicon. For these SOCs, an SOC node
|
|
should be used that defines child nodes for the devices that make
|
|
up the SOC. While platforms are not required to use this model in
|
|
order to boot the kernel, it is highly encouraged that all SOC
|
|
implementations define as complete a flat-device-tree as possible to
|
|
describe the devices on the SOC. This will allow for the
|
|
genericization of much of the kernel code.
|
|
|
|
|
|
1) Defining child nodes of an SOC
|
|
---------------------------------
|
|
|
|
Each device that is part of an SOC may have its own node entry inside
|
|
the SOC node. For each device that is included in the SOC, the unit
|
|
address property represents the address offset for this device's
|
|
memory-mapped registers in the parent's address space. The parent's
|
|
address space is defined by the "ranges" property in the top-level soc
|
|
node. The "reg" property for each node that exists directly under the
|
|
SOC node should contain the address mapping from the child address space
|
|
to the parent SOC address space and the size of the device's
|
|
memory-mapped register file.
|
|
|
|
For many devices that may exist inside an SOC, there are predefined
|
|
specifications for the format of the device tree node. All SOC child
|
|
nodes should follow these specifications, except where noted in this
|
|
document.
|
|
|
|
See appendix A for an example partial SOC node definition for the
|
|
MPC8540.
|
|
|
|
|
|
2) Specifying interrupt information for SOC devices
|
|
---------------------------------------------------
|
|
|
|
Each device that is part of an SOC and which generates interrupts
|
|
should have the following properties:
|
|
|
|
- interrupt-parent : contains the phandle of the interrupt
|
|
controller which handles interrupts for this device
|
|
- interrupts : a list of tuples representing the interrupt
|
|
number and the interrupt sense and level for each interrupt
|
|
for this device.
|
|
|
|
This information is used by the kernel to build the interrupt table
|
|
for the interrupt controllers in the system.
|
|
|
|
Sense and level information should be encoded as follows:
|
|
|
|
Devices connected to openPIC-compatible controllers should encode
|
|
sense and polarity as follows:
|
|
|
|
0 = low to high edge sensitive type enabled
|
|
1 = active low level sensitive type enabled
|
|
2 = active high level sensitive type enabled
|
|
3 = high to low edge sensitive type enabled
|
|
|
|
ISA PIC interrupt controllers should adhere to the ISA PIC
|
|
encodings listed below:
|
|
|
|
0 = active low level sensitive type enabled
|
|
1 = active high level sensitive type enabled
|
|
2 = high to low edge sensitive type enabled
|
|
3 = low to high edge sensitive type enabled
|
|
|
|
|
|
|
|
3) Representing devices without a current OF specification
|
|
----------------------------------------------------------
|
|
|
|
Currently, there are many devices on SOCs that do not have a standard
|
|
representation pre-defined as part of the open firmware
|
|
specifications, mainly because the boards that contain these SOCs are
|
|
not currently booted using open firmware. This section contains
|
|
descriptions for the SOC devices for which new nodes have been
|
|
defined; this list will expand as more and more SOC-containing
|
|
platforms are moved over to use the flattened-device-tree model.
|
|
|
|
a) MDIO IO device
|
|
|
|
The MDIO is a bus to which the PHY devices are connected. For each
|
|
device that exists on this bus, a child node should be created. See
|
|
the definition of the PHY node below for an example of how to define
|
|
a PHY.
|
|
|
|
Required properties:
|
|
- reg : Offset and length of the register set for the device
|
|
- device_type : Should be "mdio"
|
|
- compatible : Should define the compatible device type for the
|
|
mdio. Currently, this is most likely to be "gianfar"
|
|
|
|
Example:
|
|
|
|
mdio@24520 {
|
|
reg = <24520 20>;
|
|
device_type = "mdio";
|
|
compatible = "gianfar";
|
|
|
|
ethernet-phy@0 {
|
|
......
|
|
};
|
|
};
|
|
|
|
|
|
b) Gianfar-compatible ethernet nodes
|
|
|
|
Required properties:
|
|
|
|
- device_type : Should be "network"
|
|
- model : Model of the device. Can be "TSEC", "eTSEC", or "FEC"
|
|
- compatible : Should be "gianfar"
|
|
- reg : Offset and length of the register set for the device
|
|
- mac-address : List of bytes representing the ethernet address of
|
|
this controller
|
|
- interrupts : <a b> where a is the interrupt number and b is a
|
|
field that represents an encoding of the sense and level
|
|
information for the interrupt. This should be encoded based on
|
|
the information in section 2) depending on the type of interrupt
|
|
controller you have.
|
|
- interrupt-parent : the phandle for the interrupt controller that
|
|
services interrupts for this device.
|
|
- phy-handle : The phandle for the PHY connected to this ethernet
|
|
controller.
|
|
|
|
Example:
|
|
|
|
ethernet@24000 {
|
|
#size-cells = <0>;
|
|
device_type = "network";
|
|
model = "TSEC";
|
|
compatible = "gianfar";
|
|
reg = <24000 1000>;
|
|
mac-address = [ 00 E0 0C 00 73 00 ];
|
|
interrupts = <d 3 e 3 12 3>;
|
|
interrupt-parent = <40000>;
|
|
phy-handle = <2452000>
|
|
};
|
|
|
|
|
|
|
|
c) PHY nodes
|
|
|
|
Required properties:
|
|
|
|
- device_type : Should be "ethernet-phy"
|
|
- interrupts : <a b> where a is the interrupt number and b is a
|
|
field that represents an encoding of the sense and level
|
|
information for the interrupt. This should be encoded based on
|
|
the information in section 2) depending on the type of interrupt
|
|
controller you have.
|
|
- interrupt-parent : the phandle for the interrupt controller that
|
|
services interrupts for this device.
|
|
- reg : The ID number for the phy, usually a small integer
|
|
- linux,phandle : phandle for this node; likely referenced by an
|
|
ethernet controller node.
|
|
|
|
|
|
Example:
|
|
|
|
ethernet-phy@0 {
|
|
linux,phandle = <2452000>
|
|
interrupt-parent = <40000>;
|
|
interrupts = <35 1>;
|
|
reg = <0>;
|
|
device_type = "ethernet-phy";
|
|
};
|
|
|
|
|
|
d) Interrupt controllers
|
|
|
|
Some SOC devices contain interrupt controllers that are different
|
|
from the standard Open PIC specification. The SOC device nodes for
|
|
these types of controllers should be specified just like a standard
|
|
OpenPIC controller. Sense and level information should be encoded
|
|
as specified in section 2) of this chapter for each device that
|
|
specifies an interrupt.
|
|
|
|
Example :
|
|
|
|
pic@40000 {
|
|
linux,phandle = <40000>;
|
|
clock-frequency = <0>;
|
|
interrupt-controller;
|
|
#address-cells = <0>;
|
|
reg = <40000 40000>;
|
|
built-in;
|
|
compatible = "chrp,open-pic";
|
|
device_type = "open-pic";
|
|
big-endian;
|
|
};
|
|
|
|
|
|
e) I2C
|
|
|
|
Required properties :
|
|
|
|
- device_type : Should be "i2c"
|
|
- reg : Offset and length of the register set for the device
|
|
|
|
Recommended properties :
|
|
|
|
- compatible : Should be "fsl-i2c" for parts compatible with
|
|
Freescale I2C specifications.
|
|
- interrupts : <a b> where a is the interrupt number and b is a
|
|
field that represents an encoding of the sense and level
|
|
information for the interrupt. This should be encoded based on
|
|
the information in section 2) depending on the type of interrupt
|
|
controller you have.
|
|
- interrupt-parent : the phandle for the interrupt controller that
|
|
services interrupts for this device.
|
|
- dfsrr : boolean; if defined, indicates that this I2C device has
|
|
a digital filter sampling rate register
|
|
- fsl5200-clocking : boolean; if defined, indicated that this device
|
|
uses the FSL 5200 clocking mechanism.
|
|
|
|
Example :
|
|
|
|
i2c@3000 {
|
|
interrupt-parent = <40000>;
|
|
interrupts = <1b 3>;
|
|
reg = <3000 18>;
|
|
device_type = "i2c";
|
|
compatible = "fsl-i2c";
|
|
dfsrr;
|
|
};
|
|
|
|
|
|
f) Freescale SOC USB controllers
|
|
|
|
The device node for a USB controller that is part of a Freescale
|
|
SOC is as described in the document "Open Firmware Recommended
|
|
Practice : Universal Serial Bus" with the following modifications
|
|
and additions :
|
|
|
|
Required properties :
|
|
- compatible : Should be "fsl-usb2-mph" for multi port host usb
|
|
controllers, or "fsl-usb2-dr" for dual role usb controllers
|
|
- phy_type : For multi port host usb controllers, should be one of
|
|
"ulpi", or "serial". For dual role usb controllers, should be
|
|
one of "ulpi", "utmi", "utmi_wide", or "serial".
|
|
- reg : Offset and length of the register set for the device
|
|
- port0 : boolean; if defined, indicates port0 is connected for
|
|
fsl-usb2-mph compatible controllers. Either this property or
|
|
"port1" (or both) must be defined for "fsl-usb2-mph" compatible
|
|
controllers.
|
|
- port1 : boolean; if defined, indicates port1 is connected for
|
|
fsl-usb2-mph compatible controllers. Either this property or
|
|
"port0" (or both) must be defined for "fsl-usb2-mph" compatible
|
|
controllers.
|
|
- dr_mode : indicates the working mode for "fsl-usb2-dr" compatible
|
|
controllers. Can be "host", "peripheral", or "otg". Default to
|
|
"host" if not defined for backward compatibility.
|
|
|
|
Recommended properties :
|
|
- interrupts : <a b> where a is the interrupt number and b is a
|
|
field that represents an encoding of the sense and level
|
|
information for the interrupt. This should be encoded based on
|
|
the information in section 2) depending on the type of interrupt
|
|
controller you have.
|
|
- interrupt-parent : the phandle for the interrupt controller that
|
|
services interrupts for this device.
|
|
|
|
Example multi port host usb controller device node :
|
|
usb@22000 {
|
|
device_type = "usb";
|
|
compatible = "fsl-usb2-mph";
|
|
reg = <22000 1000>;
|
|
#address-cells = <1>;
|
|
#size-cells = <0>;
|
|
interrupt-parent = <700>;
|
|
interrupts = <27 1>;
|
|
phy_type = "ulpi";
|
|
port0;
|
|
port1;
|
|
};
|
|
|
|
Example dual role usb controller device node :
|
|
usb@23000 {
|
|
device_type = "usb";
|
|
compatible = "fsl-usb2-dr";
|
|
reg = <23000 1000>;
|
|
#address-cells = <1>;
|
|
#size-cells = <0>;
|
|
interrupt-parent = <700>;
|
|
interrupts = <26 1>;
|
|
dr_mode = "otg";
|
|
phy = "ulpi";
|
|
};
|
|
|
|
|
|
g) Freescale SOC SEC Security Engines
|
|
|
|
Required properties:
|
|
|
|
- device_type : Should be "crypto"
|
|
- model : Model of the device. Should be "SEC1" or "SEC2"
|
|
- compatible : Should be "talitos"
|
|
- reg : Offset and length of the register set for the device
|
|
- interrupts : <a b> where a is the interrupt number and b is a
|
|
field that represents an encoding of the sense and level
|
|
information for the interrupt. This should be encoded based on
|
|
the information in section 2) depending on the type of interrupt
|
|
controller you have.
|
|
- interrupt-parent : the phandle for the interrupt controller that
|
|
services interrupts for this device.
|
|
- num-channels : An integer representing the number of channels
|
|
available.
|
|
- channel-fifo-len : An integer representing the number of
|
|
descriptor pointers each channel fetch fifo can hold.
|
|
- exec-units-mask : The bitmask representing what execution units
|
|
(EUs) are available. It's a single 32 bit cell. EU information
|
|
should be encoded following the SEC's Descriptor Header Dword
|
|
EU_SEL0 field documentation, i.e. as follows:
|
|
|
|
bit 0 = reserved - should be 0
|
|
bit 1 = set if SEC has the ARC4 EU (AFEU)
|
|
bit 2 = set if SEC has the DES/3DES EU (DEU)
|
|
bit 3 = set if SEC has the message digest EU (MDEU)
|
|
bit 4 = set if SEC has the random number generator EU (RNG)
|
|
bit 5 = set if SEC has the public key EU (PKEU)
|
|
bit 6 = set if SEC has the AES EU (AESU)
|
|
bit 7 = set if SEC has the Kasumi EU (KEU)
|
|
|
|
bits 8 through 31 are reserved for future SEC EUs.
|
|
|
|
- descriptor-types-mask : The bitmask representing what descriptors
|
|
are available. It's a single 32 bit cell. Descriptor type
|
|
information should be encoded following the SEC's Descriptor
|
|
Header Dword DESC_TYPE field documentation, i.e. as follows:
|
|
|
|
bit 0 = set if SEC supports the aesu_ctr_nonsnoop desc. type
|
|
bit 1 = set if SEC supports the ipsec_esp descriptor type
|
|
bit 2 = set if SEC supports the common_nonsnoop desc. type
|
|
bit 3 = set if SEC supports the 802.11i AES ccmp desc. type
|
|
bit 4 = set if SEC supports the hmac_snoop_no_afeu desc. type
|
|
bit 5 = set if SEC supports the srtp descriptor type
|
|
bit 6 = set if SEC supports the non_hmac_snoop_no_afeu desc.type
|
|
bit 7 = set if SEC supports the pkeu_assemble descriptor type
|
|
bit 8 = set if SEC supports the aesu_key_expand_output desc.type
|
|
bit 9 = set if SEC supports the pkeu_ptmul descriptor type
|
|
bit 10 = set if SEC supports the common_nonsnoop_afeu desc. type
|
|
bit 11 = set if SEC supports the pkeu_ptadd_dbl descriptor type
|
|
|
|
..and so on and so forth.
|
|
|
|
Example:
|
|
|
|
/* MPC8548E */
|
|
crypto@30000 {
|
|
device_type = "crypto";
|
|
model = "SEC2";
|
|
compatible = "talitos";
|
|
reg = <30000 10000>;
|
|
interrupts = <1d 3>;
|
|
interrupt-parent = <40000>;
|
|
num-channels = <4>;
|
|
channel-fifo-len = <18>;
|
|
exec-units-mask = <000000fe>;
|
|
descriptor-types-mask = <012b0ebf>;
|
|
};
|
|
|
|
h) Board Control and Status (BCSR)
|
|
|
|
Required properties:
|
|
|
|
- device_type : Should be "board-control"
|
|
- reg : Offset and length of the register set for the device
|
|
|
|
Example:
|
|
|
|
bcsr@f8000000 {
|
|
device_type = "board-control";
|
|
reg = <f8000000 8000>;
|
|
};
|
|
|
|
i) Freescale QUICC Engine module (QE)
|
|
This represents qe module that is installed on PowerQUICC II Pro.
|
|
Hopefully it will merge backward compatibility with CPM/CPM2.
|
|
Basically, it is a bus of devices, that could act more or less
|
|
as a complete entity (UCC, USB etc ). All of them should be siblings on
|
|
the "root" qe node, using the common properties from there.
|
|
The description below applies to the the qe of MPC8360 and
|
|
more nodes and properties would be extended in the future.
|
|
|
|
i) Root QE device
|
|
|
|
Required properties:
|
|
- device_type : should be "qe";
|
|
- model : precise model of the QE, Can be "QE", "CPM", or "CPM2"
|
|
- reg : offset and length of the device registers.
|
|
- bus-frequency : the clock frequency for QUICC Engine.
|
|
|
|
Recommended properties
|
|
- brg-frequency : the internal clock source frequency for baud-rate
|
|
generators in Hz.
|
|
|
|
Example:
|
|
qe@e0100000 {
|
|
#address-cells = <1>;
|
|
#size-cells = <1>;
|
|
#interrupt-cells = <2>;
|
|
device_type = "qe";
|
|
model = "QE";
|
|
ranges = <0 e0100000 00100000>;
|
|
reg = <e0100000 480>;
|
|
brg-frequency = <0>;
|
|
bus-frequency = <179A7B00>;
|
|
}
|
|
|
|
|
|
ii) SPI (Serial Peripheral Interface)
|
|
|
|
Required properties:
|
|
- device_type : should be "spi".
|
|
- compatible : should be "fsl_spi".
|
|
- mode : the spi operation mode, it can be "cpu" or "qe".
|
|
- reg : Offset and length of the register set for the device
|
|
- interrupts : <a b> where a is the interrupt number and b is a
|
|
field that represents an encoding of the sense and level
|
|
information for the interrupt. This should be encoded based on
|
|
the information in section 2) depending on the type of interrupt
|
|
controller you have.
|
|
- interrupt-parent : the phandle for the interrupt controller that
|
|
services interrupts for this device.
|
|
|
|
Example:
|
|
spi@4c0 {
|
|
device_type = "spi";
|
|
compatible = "fsl_spi";
|
|
reg = <4c0 40>;
|
|
interrupts = <82 0>;
|
|
interrupt-parent = <700>;
|
|
mode = "cpu";
|
|
};
|
|
|
|
|
|
iii) USB (Universal Serial Bus Controller)
|
|
|
|
Required properties:
|
|
- device_type : should be "usb".
|
|
- compatible : could be "qe_udc" or "fhci-hcd".
|
|
- mode : the could be "host" or "slave".
|
|
- reg : Offset and length of the register set for the device
|
|
- interrupts : <a b> where a is the interrupt number and b is a
|
|
field that represents an encoding of the sense and level
|
|
information for the interrupt. This should be encoded based on
|
|
the information in section 2) depending on the type of interrupt
|
|
controller you have.
|
|
- interrupt-parent : the phandle for the interrupt controller that
|
|
services interrupts for this device.
|
|
|
|
Example(slave):
|
|
usb@6c0 {
|
|
device_type = "usb";
|
|
compatible = "qe_udc";
|
|
reg = <6c0 40>;
|
|
interrupts = <8b 0>;
|
|
interrupt-parent = <700>;
|
|
mode = "slave";
|
|
};
|
|
|
|
|
|
iv) UCC (Unified Communications Controllers)
|
|
|
|
Required properties:
|
|
- device_type : should be "network", "hldc", "uart", "transparent"
|
|
"bisync" or "atm".
|
|
- compatible : could be "ucc_geth" or "fsl_atm" and so on.
|
|
- model : should be "UCC".
|
|
- device-id : the ucc number(1-8), corresponding to UCCx in UM.
|
|
- reg : Offset and length of the register set for the device
|
|
- interrupts : <a b> where a is the interrupt number and b is a
|
|
field that represents an encoding of the sense and level
|
|
information for the interrupt. This should be encoded based on
|
|
the information in section 2) depending on the type of interrupt
|
|
controller you have.
|
|
- interrupt-parent : the phandle for the interrupt controller that
|
|
services interrupts for this device.
|
|
- pio-handle : The phandle for the Parallel I/O port configuration.
|
|
- rx-clock : represents the UCC receive clock source.
|
|
0x00 : clock source is disabled;
|
|
0x1~0x10 : clock source is BRG1~BRG16 respectively;
|
|
0x11~0x28: clock source is QE_CLK1~QE_CLK24 respectively.
|
|
- tx-clock: represents the UCC transmit clock source;
|
|
0x00 : clock source is disabled;
|
|
0x1~0x10 : clock source is BRG1~BRG16 respectively;
|
|
0x11~0x28: clock source is QE_CLK1~QE_CLK24 respectively.
|
|
|
|
Required properties for network device_type:
|
|
- mac-address : list of bytes representing the ethernet address.
|
|
- phy-handle : The phandle for the PHY connected to this controller.
|
|
|
|
Example:
|
|
ucc@2000 {
|
|
device_type = "network";
|
|
compatible = "ucc_geth";
|
|
model = "UCC";
|
|
device-id = <1>;
|
|
reg = <2000 200>;
|
|
interrupts = <a0 0>;
|
|
interrupt-parent = <700>;
|
|
mac-address = [ 00 04 9f 00 23 23 ];
|
|
rx-clock = "none";
|
|
tx-clock = "clk9";
|
|
phy-handle = <212000>;
|
|
pio-handle = <140001>;
|
|
};
|
|
|
|
|
|
v) Parallel I/O Ports
|
|
|
|
This node configures Parallel I/O ports for CPUs with QE support.
|
|
The node should reside in the "soc" node of the tree. For each
|
|
device that using parallel I/O ports, a child node should be created.
|
|
See the definition of the Pin configuration nodes below for more
|
|
information.
|
|
|
|
Required properties:
|
|
- device_type : should be "par_io".
|
|
- reg : offset to the register set and its length.
|
|
- num-ports : number of Parallel I/O ports
|
|
|
|
Example:
|
|
par_io@1400 {
|
|
reg = <1400 100>;
|
|
#address-cells = <1>;
|
|
#size-cells = <0>;
|
|
device_type = "par_io";
|
|
num-ports = <7>;
|
|
ucc_pin@01 {
|
|
......
|
|
};
|
|
|
|
|
|
vi) Pin configuration nodes
|
|
|
|
Required properties:
|
|
- linux,phandle : phandle of this node; likely referenced by a QE
|
|
device.
|
|
- pio-map : array of pin configurations. Each pin is defined by 6
|
|
integers. The six numbers are respectively: port, pin, dir,
|
|
open_drain, assignment, has_irq.
|
|
- port : port number of the pin; 0-6 represent port A-G in UM.
|
|
- pin : pin number in the port.
|
|
- dir : direction of the pin, should encode as follows:
|
|
|
|
0 = The pin is disabled
|
|
1 = The pin is an output
|
|
2 = The pin is an input
|
|
3 = The pin is I/O
|
|
|
|
- open_drain : indicates the pin is normal or wired-OR:
|
|
|
|
0 = The pin is actively driven as an output
|
|
1 = The pin is an open-drain driver. As an output, the pin is
|
|
driven active-low, otherwise it is three-stated.
|
|
|
|
- assignment : function number of the pin according to the Pin Assignment
|
|
tables in User Manual. Each pin can have up to 4 possible functions in
|
|
QE and two options for CPM.
|
|
- has_irq : indicates if the pin is used as source of exteral
|
|
interrupts.
|
|
|
|
Example:
|
|
ucc_pin@01 {
|
|
linux,phandle = <140001>;
|
|
pio-map = <
|
|
/* port pin dir open_drain assignment has_irq */
|
|
0 3 1 0 1 0 /* TxD0 */
|
|
0 4 1 0 1 0 /* TxD1 */
|
|
0 5 1 0 1 0 /* TxD2 */
|
|
0 6 1 0 1 0 /* TxD3 */
|
|
1 6 1 0 3 0 /* TxD4 */
|
|
1 7 1 0 1 0 /* TxD5 */
|
|
1 9 1 0 2 0 /* TxD6 */
|
|
1 a 1 0 2 0 /* TxD7 */
|
|
0 9 2 0 1 0 /* RxD0 */
|
|
0 a 2 0 1 0 /* RxD1 */
|
|
0 b 2 0 1 0 /* RxD2 */
|
|
0 c 2 0 1 0 /* RxD3 */
|
|
0 d 2 0 1 0 /* RxD4 */
|
|
1 1 2 0 2 0 /* RxD5 */
|
|
1 0 2 0 2 0 /* RxD6 */
|
|
1 4 2 0 2 0 /* RxD7 */
|
|
0 7 1 0 1 0 /* TX_EN */
|
|
0 8 1 0 1 0 /* TX_ER */
|
|
0 f 2 0 1 0 /* RX_DV */
|
|
0 10 2 0 1 0 /* RX_ER */
|
|
0 0 2 0 1 0 /* RX_CLK */
|
|
2 9 1 0 3 0 /* GTX_CLK - CLK10 */
|
|
2 8 2 0 1 0>; /* GTX125 - CLK9 */
|
|
};
|
|
|
|
vii) Multi-User RAM (MURAM)
|
|
|
|
Required properties:
|
|
- device_type : should be "muram".
|
|
- mode : the could be "host" or "slave".
|
|
- ranges : Should be defined as specified in 1) to describe the
|
|
translation of MURAM addresses.
|
|
- data-only : sub-node which defines the address area under MURAM
|
|
bus that can be allocated as data/parameter
|
|
|
|
Example:
|
|
|
|
muram@10000 {
|
|
device_type = "muram";
|
|
ranges = <0 00010000 0000c000>;
|
|
|
|
data-only@0{
|
|
reg = <0 c000>;
|
|
};
|
|
};
|
|
|
|
g) Flash chip nodes
|
|
|
|
Flash chips (Memory Technology Devices) are often used for solid state
|
|
file systems on embedded devices.
|
|
|
|
Required properties:
|
|
|
|
- device_type : has to be "rom"
|
|
- compatible : Should specify what this flash device is compatible with.
|
|
Currently, this is most likely to be "direct-mapped" (which
|
|
corresponds to the MTD physmap mapping driver).
|
|
- reg : Offset and length of the register set (or memory mapping) for
|
|
the device.
|
|
- bank-width : Width of the flash data bus in bytes. Required
|
|
for the NOR flashes (compatible == "direct-mapped" and others) ONLY.
|
|
|
|
Recommended properties :
|
|
|
|
- partitions : Several pairs of 32-bit values where the first value is
|
|
partition's offset from the start of the device and the second one is
|
|
partition size in bytes with LSB used to signify a read only
|
|
partition (so, the parition size should always be an even number).
|
|
- partition-names : The list of concatenated zero terminated strings
|
|
representing the partition names.
|
|
- probe-type : The type of probe which should be done for the chip
|
|
(JEDEC vs CFI actually). Valid ONLY for NOR flashes.
|
|
|
|
Example:
|
|
|
|
flash@ff000000 {
|
|
device_type = "rom";
|
|
compatible = "direct-mapped";
|
|
probe-type = "CFI";
|
|
reg = <ff000000 01000000>;
|
|
bank-width = <4>;
|
|
partitions = <00000000 00f80000
|
|
00f80000 00080001>;
|
|
partition-names = "fs\0firmware";
|
|
};
|
|
|
|
More devices will be defined as this spec matures.
|
|
|
|
|
|
Appendix A - Sample SOC node for MPC8540
|
|
========================================
|
|
|
|
Note that the #address-cells and #size-cells for the SoC node
|
|
in this example have been explicitly listed; these are likely
|
|
not necessary as they are usually the same as the root node.
|
|
|
|
soc8540@e0000000 {
|
|
#address-cells = <1>;
|
|
#size-cells = <1>;
|
|
#interrupt-cells = <2>;
|
|
device_type = "soc";
|
|
ranges = <00000000 e0000000 00100000>
|
|
reg = <e0000000 00003000>;
|
|
bus-frequency = <0>;
|
|
|
|
mdio@24520 {
|
|
reg = <24520 20>;
|
|
device_type = "mdio";
|
|
compatible = "gianfar";
|
|
|
|
ethernet-phy@0 {
|
|
linux,phandle = <2452000>
|
|
interrupt-parent = <40000>;
|
|
interrupts = <35 1>;
|
|
reg = <0>;
|
|
device_type = "ethernet-phy";
|
|
};
|
|
|
|
ethernet-phy@1 {
|
|
linux,phandle = <2452001>
|
|
interrupt-parent = <40000>;
|
|
interrupts = <35 1>;
|
|
reg = <1>;
|
|
device_type = "ethernet-phy";
|
|
};
|
|
|
|
ethernet-phy@3 {
|
|
linux,phandle = <2452002>
|
|
interrupt-parent = <40000>;
|
|
interrupts = <35 1>;
|
|
reg = <3>;
|
|
device_type = "ethernet-phy";
|
|
};
|
|
|
|
};
|
|
|
|
ethernet@24000 {
|
|
#size-cells = <0>;
|
|
device_type = "network";
|
|
model = "TSEC";
|
|
compatible = "gianfar";
|
|
reg = <24000 1000>;
|
|
mac-address = [ 00 E0 0C 00 73 00 ];
|
|
interrupts = <d 3 e 3 12 3>;
|
|
interrupt-parent = <40000>;
|
|
phy-handle = <2452000>;
|
|
};
|
|
|
|
ethernet@25000 {
|
|
#address-cells = <1>;
|
|
#size-cells = <0>;
|
|
device_type = "network";
|
|
model = "TSEC";
|
|
compatible = "gianfar";
|
|
reg = <25000 1000>;
|
|
mac-address = [ 00 E0 0C 00 73 01 ];
|
|
interrupts = <13 3 14 3 18 3>;
|
|
interrupt-parent = <40000>;
|
|
phy-handle = <2452001>;
|
|
};
|
|
|
|
ethernet@26000 {
|
|
#address-cells = <1>;
|
|
#size-cells = <0>;
|
|
device_type = "network";
|
|
model = "FEC";
|
|
compatible = "gianfar";
|
|
reg = <26000 1000>;
|
|
mac-address = [ 00 E0 0C 00 73 02 ];
|
|
interrupts = <19 3>;
|
|
interrupt-parent = <40000>;
|
|
phy-handle = <2452002>;
|
|
};
|
|
|
|
serial@4500 {
|
|
device_type = "serial";
|
|
compatible = "ns16550";
|
|
reg = <4500 100>;
|
|
clock-frequency = <0>;
|
|
interrupts = <1a 3>;
|
|
interrupt-parent = <40000>;
|
|
};
|
|
|
|
pic@40000 {
|
|
linux,phandle = <40000>;
|
|
clock-frequency = <0>;
|
|
interrupt-controller;
|
|
#address-cells = <0>;
|
|
reg = <40000 40000>;
|
|
built-in;
|
|
compatible = "chrp,open-pic";
|
|
device_type = "open-pic";
|
|
big-endian;
|
|
};
|
|
|
|
i2c@3000 {
|
|
interrupt-parent = <40000>;
|
|
interrupts = <1b 3>;
|
|
reg = <3000 18>;
|
|
device_type = "i2c";
|
|
compatible = "fsl-i2c";
|
|
dfsrr;
|
|
};
|
|
|
|
};
|