Documentation: Add MCB documentation
Add basic introductory documentation for the MEN Chameleon Bus. Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Johannes Thumshirn
Jonathan Corbet
Родитель
9e1aa7c888
Коммит
b9f2f4594c
|
|
@ -0,0 +1,162 @@
|
|||
MEN Chameleon Bus
|
||||
=================
|
||||
|
||||
Table of Contents
|
||||
=================
|
||||
1 Introduction
|
||||
1.1 Scope of this Document
|
||||
1.2 Limitations of the current implementation
|
||||
2 Architecture
|
||||
2.1 MEN Chameleon Bus
|
||||
2.2 Carrier Devices
|
||||
2.3 Parser
|
||||
3 Resource handling
|
||||
3.1 Memory Resources
|
||||
3.2 IRQs
|
||||
4 Writing a MCB driver
|
||||
4.1 The driver structure
|
||||
4.2 Probing and attaching
|
||||
4.3 Initializing the driver
|
||||
|
||||
|
||||
1 Introduction
|
||||
===============
|
||||
This document describes the architecture and implementation of the MEN
|
||||
Chameleon Bus (called MCB throughout this document).
|
||||
|
||||
1.1 Scope of this Document
|
||||
---------------------------
|
||||
This document is intended to be a short overview of the current
|
||||
implementation and does by no means describe to complete possibilities of MCB
|
||||
based devices.
|
||||
|
||||
1.2 Limitations of the current implementation
|
||||
----------------------------------------------
|
||||
The current implementation is limited to PCI and PCIe based carrier devices
|
||||
that only use a single memory resource and share the PCI legacy IRQ. Not
|
||||
implemented are:
|
||||
- Multi-resource MCB devices like the VME Controller or M-Module carrier.
|
||||
- MCB devices that need another MCB device, like SRAM for a DMA Controller's
|
||||
buffer descriptors or a video controller's video memory.
|
||||
- A per-carrier IRQ domain for carrier devices that have one (or more) IRQs
|
||||
per MCB device like PCIe based carriers with MSI or MSI-X support.
|
||||
|
||||
2 Architecture
|
||||
===============
|
||||
MCB is divided in 3 functional blocks:
|
||||
- The MEN Chameleon Bus itself,
|
||||
- drivers for MCB Carrier Devices and
|
||||
- the parser for the Chameleon table.
|
||||
|
||||
2.1 MEN Chameleon Bus
|
||||
----------------------
|
||||
The MEN Chameleon Bus is an artificial bus system that attaches to an MEN
|
||||
Chameleon FPGA device. These devices are multi-function devices implemented
|
||||
in a single FPGA and usually attached via some sort of PCI or PCIe link. Each
|
||||
FPGA contains a header section describing the content of the FPGA. The header
|
||||
lists the device id, PCI BAR, offset from the beginning of the PCI BAR, size
|
||||
in the FPGA, interrupt number and some other properties currently not handled
|
||||
by the MCB implementation.
|
||||
|
||||
2.2 Carrier Devices
|
||||
--------------------
|
||||
A carrier device is just an abstraction for the real world physical bus the
|
||||
chameleon FPGA is attached to. Some IP Core drivers may need to interact with
|
||||
properties of the carrier device (like querying the IRQ number of a PCI
|
||||
device). To provide abstraction from the real hardware bus, an MCB carrier
|
||||
device provides callback methods to translate the driver's MCB function calls
|
||||
to hardware related function calls. For example a carrier device may
|
||||
implement the get_irq() method which can be translate into a hardware bus
|
||||
query for the IRQ number the device should use.
|
||||
|
||||
2.3 Parser
|
||||
-----------
|
||||
The parser reads the 1st 512 bytes of a chameleon device and parses the
|
||||
chameleon table. Currently the parser only supports the Chameleon v2 variant
|
||||
of the chameleon table but can easily be adopted to support an older or
|
||||
possible future variant. While parsing the table's entries new MCB devices
|
||||
are allocated and their resources are assigned according to the resource
|
||||
assignment in the chameleon table. After resource assignment is finished, the
|
||||
MCB devices are registered at the MCB and thus at the driver core of the
|
||||
Linux kernel.
|
||||
|
||||
3 Resource handling
|
||||
====================
|
||||
The current implementation assigns exactly one memory and one IRQ resource
|
||||
per MCB device. But this is likely going to change in the future.
|
||||
|
||||
3.1 Memory Resources
|
||||
---------------------
|
||||
Each MCB device has exactly one memory resource, which can be requested from
|
||||
the MCB bus. This memory resource is the physical address of the MCB device
|
||||
inside the carrier and is intended to be passed to ioremap() and friends. It
|
||||
is already requested from the kernel by calling request_mem_region().
|
||||
|
||||
3.2 IRQs
|
||||
---------
|
||||
Each MCB device has exactly one IRQ resource, which can be requested from the
|
||||
MCB bus. If a carrier device driver implements the ->get_irq() callback
|
||||
method, the IRQ number assigned by the carrier device will be returned,
|
||||
otherwise the IRQ number inside the chameleon table will be returned. This
|
||||
number is suitable to be passed to request_irq().
|
||||
|
||||
4 Writing a MCB driver
|
||||
=======================
|
||||
|
||||
4.1 The driver structure
|
||||
-------------------------
|
||||
Each MCB driver has a structure to identify the device driver as well as
|
||||
device ids which identify the IP Core inside the FPGA. The driver structure
|
||||
also contaings callback methods which get executed on driver probe and
|
||||
removal from the system.
|
||||
|
||||
|
||||
static const struct mcb_device_id foo_ids[] = {
|
||||
{ .device = 0x123 },
|
||||
{ }
|
||||
};
|
||||
MODULE_DEVICE_TABLE(mcb, foo_ids);
|
||||
|
||||
static struct mcb_driver foo_driver = {
|
||||
driver = {
|
||||
.name = "foo-bar",
|
||||
.owner = THIS_MODULE,
|
||||
},
|
||||
.probe = foo_probe,
|
||||
.remove = foo_remove,
|
||||
.id_table = foo_ids,
|
||||
};
|
||||
|
||||
4.2 Probing and attaching
|
||||
--------------------------
|
||||
When a driver is loaded and the MCB devices it services are found, the MCB
|
||||
core will call the driver's probe callback method. When the driver is removed
|
||||
from the system, the MCB core will call the driver's remove callback method.
|
||||
|
||||
|
||||
static init foo_probe(struct mcb_device *mdev, const struct mcb_device_id *id);
|
||||
static void foo_remove(struct mcb_device *mdev);
|
||||
|
||||
4.3 Initializing the driver
|
||||
----------------------------
|
||||
When the kernel is booted or your foo driver module is inserted, you have to
|
||||
perform driver initialization. Usually it is enough to register your driver
|
||||
module at the MCB core.
|
||||
|
||||
|
||||
static int __init foo_init(void)
|
||||
{
|
||||
return mcb_register_driver(&foo_driver);
|
||||
}
|
||||
module_init(foo_init);
|
||||
|
||||
static void __exit foo_exit(void)
|
||||
{
|
||||
mcb_unregister_driver(&foo_driver);
|
||||
}
|
||||
module_exit(foo_exit);
|
||||
|
||||
The module_mcb_driver() macro can be used to reduce the above code.
|
||||
|
||||
|
||||
module_mcb_driver(foo_driver);
|
||||
|
|
@ -6665,6 +6665,7 @@ M: Johannes Thumshirn <morbidrsa@gmail.com>
|
|||
S: Maintained
|
||||
F: drivers/mcb/
|
||||
F: include/linux/mcb.h
|
||||
F: Documentation/men-chameleon-bus.txt
|
||||
|
||||
MEN F21BMC (Board Management Controller)
|
||||
M: Andreas Werner <andreas.werner@men.de>
|
||||
|
|
|
|||
Загрузка…
Ссылка в новой задаче