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Merge branch 'docs/docbook/drm' of git://github.com/mfwitten/linux into docs-move

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Randy Dunlap 2011-11-06 21:40:22 -08:00
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308
Documentation/DocBook/drm.tmpl
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@ -32,7 +32,7 @@
The Linux DRM layer contains code intended to support the needs
of complex graphics devices, usually containing programmable
pipelines well suited to 3D graphics acceleration. Graphics
drivers in the kernel can make use of DRM functions to make
drivers in the kernel may make use of DRM functions to make
tasks like memory management, interrupt handling and DMA easier,
and provide a uniform interface to applications.
</para>
@ -57,10 +57,10 @@
existing drivers.
</para>
<para>
First, we'll go over some typical driver initialization
First, we go over some typical driver initialization
requirements, like setting up command buffers, creating an
initial output configuration, and initializing core services.
Subsequent sections will cover core internals in more detail,
Subsequent sections cover core internals in more detail,
providing implementation notes and examples.
</para>
<para>
@ -74,7 +74,7 @@
</para>
<para>
The core of every DRM driver is struct drm_driver. Drivers
will typically statically initialize a drm_driver structure,
typically statically initialize a drm_driver structure,
then pass it to drm_init() at load time.
</para>
@ -88,8 +88,8 @@
</para>
<programlisting>
static struct drm_driver driver = {
/* don't use mtrr's here, the Xserver or user space app should
* deal with them for intel hardware.
/* Don't use MTRRs here; the Xserver or userspace app should
* deal with them for Intel hardware.
*/
.driver_features =
DRIVER_USE_AGP | DRIVER_REQUIRE_AGP |
@ -154,8 +154,8 @@
</programlisting>
<para>
In the example above, taken from the i915 DRM driver, the driver
sets several flags indicating what core features it supports.
We'll go over the individual callbacks in later sections. Since
sets several flags indicating what core features it supports;
we go over the individual callbacks in later sections. Since
flags indicate which features your driver supports to the DRM
core, you need to set most of them prior to calling drm_init(). Some,
like DRIVER_MODESET can be set later based on user supplied parameters,
@ -203,8 +203,8 @@
<term>DRIVER_HAVE_IRQ</term><term>DRIVER_IRQ_SHARED</term>
<listitem>
<para>
DRIVER_HAVE_IRQ indicates whether the driver has a IRQ
handler, DRIVER_IRQ_SHARED indicates whether the device &amp;
DRIVER_HAVE_IRQ indicates whether the driver has an IRQ
handler. DRIVER_IRQ_SHARED indicates whether the device &amp;
handler support shared IRQs (note that this is required of
PCI drivers).
</para>
@ -214,8 +214,8 @@
<term>DRIVER_DMA_QUEUE</term>
<listitem>
<para>
If the driver queues DMA requests and completes them
asynchronously, this flag should be set. Deprecated.
Should be set if the driver queues DMA requests and completes them
asynchronously. Deprecated.
</para>
</listitem>
</varlistentry>
@ -238,7 +238,7 @@
</variablelist>
<para>
In this specific case, the driver requires AGP and supports
IRQs. DMA, as we'll see, is handled by device specific ioctls
IRQs. DMA, as discussed later, is handled by device-specific ioctls
in this case. It also supports the kernel mode setting APIs, though
unlike in the actual i915 driver source, this example unconditionally
exports KMS capability.
@ -269,36 +269,34 @@
initial output configuration.
</para>
<para>
Note that the tasks performed at driver load time must not
conflict with DRM client requirements. For instance, if user
If compatibility is a concern (e.g. with drivers converted over
to the new interfaces from the old ones), care must be taken to
prevent device initialization and control that is incompatible with
currently active userspace drivers. For instance, if user
level mode setting drivers are in use, it would be problematic
to perform output discovery &amp; configuration at load time.
Likewise, if pre-memory management aware user level drivers are
Likewise, if user-level drivers unaware of memory management are
in use, memory management and command buffer setup may need to
be omitted. These requirements are driver specific, and care
be omitted. These requirements are driver-specific, and care
needs to be taken to keep both old and new applications and
libraries working. The i915 driver supports the "modeset"
module parameter to control whether advanced features are
enabled at load time or in legacy fashion. If compatibility is
a concern (e.g. with drivers converted over to the new interfaces
from the old ones), care must be taken to prevent incompatible
device initialization and control with the currently active
userspace drivers.
enabled at load time or in legacy fashion.
</para>
<sect2>
<title>Driver private &amp; performance counters</title>
<para>
The driver private hangs off the main drm_device structure and
can be used for tracking various device specific bits of
can be used for tracking various device-specific bits of
information, like register offsets, command buffer status,
register state for suspend/resume, etc. At load time, a
driver can simply allocate one and set drm_device.dev_priv
appropriately; at unload the driver can free it and set
drm_device.dev_priv to NULL.
driver may simply allocate one and set drm_device.dev_priv
appropriately; it should be freed and drm_device.dev_priv set
to NULL when the driver is unloaded.
</para>
<para>
The DRM supports several counters which can be used for rough
The DRM supports several counters which may be used for rough
performance characterization. Note that the DRM stat counter
system is not often used by applications, and supporting
additional counters is completely optional.
@ -307,15 +305,15 @@
These interfaces are deprecated and should not be used. If performance
monitoring is desired, the developer should investigate and
potentially enhance the kernel perf and tracing infrastructure to export
GPU related performance information to performance monitoring
tools and applications.
GPU related performance information for consumption by performance
monitoring tools and applications.
</para>
</sect2>
<sect2>
<title>Configuring the device</title>
<para>
Obviously, device configuration will be device specific.
Obviously, device configuration is device-specific.
However, there are several common operations: finding a
device's PCI resources, mapping them, and potentially setting
up an IRQ handler.
@ -323,10 +321,10 @@
<para>
Finding &amp; mapping resources is fairly straightforward. The
DRM wrapper functions, drm_get_resource_start() and
drm_get_resource_len() can be used to find BARs on the given
drm_get_resource_len(), may be used to find BARs on the given
drm_device struct. Once those values have been retrieved, the
driver load function can call drm_addmap() to create a new
mapping for the BAR in question. Note you'll probably want a
mapping for the BAR in question. Note that you probably want a
drm_local_map_t in your driver private structure to track any
mappings you create.
<!-- !Fdrivers/gpu/drm/drm_bufs.c drm_get_resource_* -->
@ -335,20 +333,20 @@
<para>
if compatibility with other operating systems isn't a concern
(DRM drivers can run under various BSD variants and OpenSolaris),
native Linux calls can be used for the above, e.g. pci_resource_*
native Linux calls may be used for the above, e.g. pci_resource_*
and iomap*/iounmap. See the Linux device driver book for more
info.
</para>
<para>
Once you have a register map, you can use the DRM_READn() and
Once you have a register map, you may use the DRM_READn() and
DRM_WRITEn() macros to access the registers on your device, or
use driver specific versions to offset into your MMIO space
relative to a driver specific base pointer (see I915_READ for
example).
use driver-specific versions to offset into your MMIO space
relative to a driver-specific base pointer (see I915_READ for
an example).
</para>
<para>
If your device supports interrupt generation, you may want to
setup an interrupt handler at driver load time as well. This
set up an interrupt handler when the driver is loaded. This
is done using the drm_irq_install() function. If your device
supports vertical blank interrupts, it should call
drm_vblank_init() to initialize the core vblank handling code before
@ -357,7 +355,7 @@
</para>
<!--!Fdrivers/char/drm/drm_irq.c drm_irq_install-->
<para>
Once your interrupt handler is registered (it'll use your
Once your interrupt handler is registered (it uses your
drm_driver.irq_handler as the actual interrupt handling
function), you can safely enable interrupts on your device,
assuming any other state your interrupt handler uses is also
@ -371,10 +369,10 @@
using the pci_map_rom() call, a convenience function that
takes care of mapping the actual ROM, whether it has been
shadowed into memory (typically at address 0xc0000) or exists
on the PCI device in the ROM BAR. Note that once you've
mapped the ROM and extracted any necessary information, be
sure to unmap it; on many devices the ROM address decoder is
shared with other BARs, so leaving it mapped can cause
on the PCI device in the ROM BAR. Note that after the ROM
has been mapped and any necessary information has been extracted,
it should be unmapped; on many devices, the ROM address decoder is
shared with other BARs, so leaving it mapped could cause
undesired behavior like hangs or memory corruption.
<!--!Fdrivers/pci/rom.c pci_map_rom-->
</para>
@ -389,9 +387,9 @@
should support a memory manager.
</para>
<para>
If your driver supports memory management (it should!), you'll
If your driver supports memory management (it should!), you
need to set that up at load time as well. How you initialize
it depends on which memory manager you're using, TTM or GEM.
it depends on which memory manager you're using: TTM or GEM.
</para>
<sect3>
<title>TTM initialization</title>
@ -401,7 +399,7 @@
and devices with dedicated video RAM (VRAM), i.e. most discrete
graphics devices. If your device has dedicated RAM, supporting
TTM is desirable. TTM also integrates tightly with your
driver specific buffer execution function. See the radeon
driver-specific buffer execution function. See the radeon
driver for examples.
</para>
<para>
@ -429,21 +427,21 @@
created by the memory manager at runtime. Your global TTM should
have a type of TTM_GLOBAL_TTM_MEM. The size field for the global
object should be sizeof(struct ttm_mem_global), and the init and
release hooks should point at your driver specific init and
release routines, which will probably eventually call
ttm_mem_global_init and ttm_mem_global_release respectively.
release hooks should point at your driver-specific init and
release routines, which probably eventually call
ttm_mem_global_init and ttm_mem_global_release, respectively.
</para>
<para>
Once your global TTM accounting structure is set up and initialized
(done by calling ttm_global_item_ref on the global object you
just created), you'll need to create a buffer object TTM to
by calling ttm_global_item_ref() on it,
you need to create a buffer object TTM to
provide a pool for buffer object allocation by clients and the
kernel itself. The type of this object should be TTM_GLOBAL_TTM_BO,
and its size should be sizeof(struct ttm_bo_global). Again,
driver specific init and release functions can be provided,
likely eventually calling ttm_bo_global_init and
ttm_bo_global_release, respectively. Also like the previous
object, ttm_global_item_ref is used to create an initial reference
driver-specific init and release functions may be provided,
likely eventually calling ttm_bo_global_init() and
ttm_bo_global_release(), respectively. Also, like the previous
object, ttm_global_item_ref() is used to create an initial reference
count for the TTM, which will call your initialization function.
</para>
</sect3>
@ -453,27 +451,26 @@
GEM is an alternative to TTM, designed specifically for UMA
devices. It has simpler initialization and execution requirements
than TTM, but has no VRAM management capability. Core GEM
initialization is comprised of a basic drm_mm_init call to create
is initialized by calling drm_mm_init() to create
a GTT DRM MM object, which provides an address space pool for
object allocation. In a KMS configuration, the driver will
need to allocate and initialize a command ring buffer following
basic GEM initialization. Most UMA devices have a so-called
object allocation. In a KMS configuration, the driver
needs to allocate and initialize a command ring buffer following
core GEM initialization. A UMA device usually has what is called a
"stolen" memory region, which provides space for the initial
framebuffer and large, contiguous memory regions required by the
device. This space is not typically managed by GEM, and must
device. This space is not typically managed by GEM, and it must
be initialized separately into its own DRM MM object.
</para>
<para>
Initialization will be driver specific, and will depend on
the architecture of the device. In the case of Intel
Initialization is driver-specific. In the case of Intel
integrated graphics chips like 965GM, GEM initialization can
be done by calling the internal GEM init function,
i915_gem_do_init(). Since the 965GM is a UMA device
(i.e. it doesn't have dedicated VRAM), GEM will manage
(i.e. it doesn't have dedicated VRAM), GEM manages
making regular RAM available for GPU operations. Memory set
aside by the BIOS (called "stolen" memory by the i915
driver) will be managed by the DRM memrange allocator; the
rest of the aperture will be managed by GEM.
driver) is managed by the DRM memrange allocator; the
rest of the aperture is managed by GEM.
<programlisting>
/* Basic memrange allocator for stolen space (aka vram) */
drm_memrange_init(&amp;dev_priv->vram, 0, prealloc_size);
@ -483,7 +480,7 @@
<!--!Edrivers/char/drm/drm_memrange.c-->
</para>
<para>
Once the memory manager has been set up, we can allocate the
Once the memory manager has been set up, we may allocate the
command buffer. In the i915 case, this is also done with a
GEM function, i915_gem_init_ringbuffer().
</para>
@ -493,16 +490,25 @@
<sect2>
<title>Output configuration</title>
<para>
The final initialization task is output configuration. This involves
finding and initializing the CRTCs, encoders and connectors
for your device, creating an initial configuration and
registering a framebuffer console driver.
The final initialization task is output configuration. This involves:
<itemizedlist>
<listitem>
Finding and initializing the CRTCs, encoders, and connectors
for the device.
</listitem>
<listitem>
Creating an initial configuration.
</listitem>
<listitem>
Registering a framebuffer console driver.
</listitem>
</itemizedlist>
</para>
<sect3>
<title>Output discovery and initialization</title>
<para>
Several core functions exist to create CRTCs, encoders and
connectors, namely drm_crtc_init(), drm_connector_init() and
Several core functions exist to create CRTCs, encoders, and
connectors, namely: drm_crtc_init(), drm_connector_init(), and
drm_encoder_init(), along with several "helper" functions to
perform common tasks.
</para>
@ -555,10 +561,10 @@ void intel_crt_init(struct drm_device *dev)
</programlisting>
<para>
In the example above (again, taken from the i915 driver), a
CRT connector and encoder combination is created. A device
specific i2c bus is also created, for fetching EDID data and
CRT connector and encoder combination is created. A device-specific
i2c bus is also created for fetching EDID data and
performing monitor detection. Once the process is complete,
the new connector is registered with sysfs, to make its
the new connector is registered with sysfs to make its
properties available to applications.
</para>
<sect4>
@ -567,12 +573,12 @@ void intel_crt_init(struct drm_device *dev)
Since many PC-class graphics devices have similar display output
designs, the DRM provides a set of helper functions to make
output management easier. The core helper routines handle
encoder re-routing and disabling of unused functions following
mode set. Using the helpers is optional, but recommended for
encoder re-routing and the disabling of unused functions following
mode setting. Using the helpers is optional, but recommended for
devices with PC-style architectures (i.e. a set of display planes
for feeding pixels to encoders which are in turn routed to
connectors). Devices with more complex requirements needing
finer grained management can opt to use the core callbacks
finer grained management may opt to use the core callbacks
directly.
</para>
<para>
@ -580,17 +586,25 @@ void intel_crt_init(struct drm_device *dev)
</para>
</sect4>
<para>
For each encoder, CRTC and connector, several functions must
be provided, depending on the object type. Encoder objects
need to provide a DPMS (basically on/off) function, mode fixup
(for converting requested modes into native hardware timings),
and prepare, set and commit functions for use by the core DRM
helper functions. Connector helpers need to provide mode fetch and
validity functions as well as an encoder matching function for
returning an ideal encoder for a given connector. The core
connector functions include a DPMS callback, (deprecated)
save/restore routines, detection, mode probing, property handling,
and cleanup functions.
Each encoder object needs to provide:
<itemizedlist>
<listitem>
A DPMS (basically on/off) function.
</listitem>
<listitem>
A mode-fixup function (for converting requested modes into
native hardware timings).
</listitem>
<listitem>
Functions (prepare, set, and commit) for use by the core DRM
helper functions.
</listitem>
</itemizedlist>
Connector helpers need to provide functions (mode-fetch, validity,
and encoder-matching) for returning an ideal encoder for a given
connector. The core connector functions include a DPMS callback,
save/restore routines (deprecated), detection, mode probing,
property handling, and cleanup functions.
</para>
<!--!Edrivers/char/drm/drm_crtc.h-->
<!--!Edrivers/char/drm/drm_crtc.c-->
@ -605,22 +619,33 @@ void intel_crt_init(struct drm_device *dev)
<title>VBlank event handling</title>
<para>
The DRM core exposes two vertical blank related ioctls:
DRM_IOCTL_WAIT_VBLANK and DRM_IOCTL_MODESET_CTL.
<variablelist>
<varlistentry>
<term>DRM_IOCTL_WAIT_VBLANK</term>
<listitem>
<para>
This takes a struct drm_wait_vblank structure as its argument,
and it is used to block or request a signal when a specified
vblank event occurs.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>DRM_IOCTL_MODESET_CTL</term>
<listitem>
<para>
This should be called by application level drivers before and
after mode setting, since on many devices the vertical blank
counter is reset at that time. Internally, the DRM snapshots
the last vblank count when the ioctl is called with the
_DRM_PRE_MODESET command, so that the counter won't go backwards
(which is dealt with when _DRM_POST_MODESET is used).
</para>
</listitem>
</varlistentry>
</variablelist>
<!--!Edrivers/char/drm/drm_irq.c-->
</para>
<para>
DRM_IOCTL_WAIT_VBLANK takes a struct drm_wait_vblank structure
as its argument, and is used to block or request a signal when a
specified vblank event occurs.
</para>
<para>
DRM_IOCTL_MODESET_CTL should be called by application level
drivers before and after mode setting, since on many devices the
vertical blank counter will be reset at that time. Internally,
the DRM snapshots the last vblank count when the ioctl is called
with the _DRM_PRE_MODESET command so that the counter won't go
backwards (which is dealt with when _DRM_POST_MODESET is used).
</para>
<para>
To support the functions above, the DRM core provides several
helper functions for tracking vertical blank counters, and
@ -632,24 +657,24 @@ void intel_crt_init(struct drm_device *dev)
register. The enable and disable vblank callbacks should enable
and disable vertical blank interrupts, respectively. In the
absence of DRM clients waiting on vblank events, the core DRM
code will use the disable_vblank() function to disable
interrupts, which saves power. They'll be re-enabled again when
code uses the disable_vblank() function to disable
interrupts, which saves power. They are re-enabled again when
a client calls the vblank wait ioctl above.
</para>
<para>
Devices that don't provide a count register can simply use an
A device that doesn't provide a count register may simply use an
internal atomic counter incremented on every vertical blank
interrupt, and can make their enable and disable vblank
functions into no-ops.
interrupt (and then treat the enable_vblank() and disable_vblank()
callbacks as no-ops).
</para>
</sect1>
<sect1>
<title>Memory management</title>
<para>
The memory manager lies at the heart of many DRM operations, and
is also required to support advanced client features like OpenGL
pbuffers. The DRM currently contains two memory managers, TTM
The memory manager lies at the heart of many DRM operations; it
is required to support advanced client features like OpenGL
pbuffers. The DRM currently contains two memory managers: TTM
and GEM.
</para>
@ -679,41 +704,46 @@ void intel_crt_init(struct drm_device *dev)
<para>
GEM-enabled drivers must provide gem_init_object() and
gem_free_object() callbacks to support the core memory
allocation routines. They should also provide several driver
specific ioctls to support command execution, pinning, buffer
allocation routines. They should also provide several driver-specific
ioctls to support command execution, pinning, buffer
read &amp; write, mapping, and domain ownership transfers.
</para>
<para>
On a fundamental level, GEM involves several operations: memory
allocation and freeing, command execution, and aperture management
at command execution time. Buffer object allocation is relatively
On a fundamental level, GEM involves several operations:
<itemizedlist>
<listitem>Memory allocation and freeing</listitem>
<listitem>Command execution</listitem>
<listitem>Aperture management at command execution time</listitem>
</itemizedlist>
Buffer object allocation is relatively
straightforward and largely provided by Linux's shmem layer, which
provides memory to back each object. When mapped into the GTT
or used in a command buffer, the backing pages for an object are
flushed to memory and marked write combined so as to be coherent
with the GPU. Likewise, when the GPU finishes rendering to an object,
if the CPU accesses it, it must be made coherent with the CPU's view
with the GPU. Likewise, if the CPU accesses an object after the GPU
has finished rendering to the object, then the object must be made
coherent with the CPU's view
of memory, usually involving GPU cache flushing of various kinds.
This core CPU&lt;-&gt;GPU coherency management is provided by the GEM
set domain function, which evaluates an object's current domain and
This core CPU&lt;-&gt;GPU coherency management is provided by a
device-specific ioctl, which evaluates an object's current domain and
performs any necessary flushing or synchronization to put the object
into the desired coherency domain (note that the object may be busy,
i.e. an active render target; in that case the set domain function
will block the client and wait for rendering to complete before
i.e. an active render target; in that case, setting the domain
blocks the client and waits for rendering to complete before
performing any necessary flushing operations).
</para>
<para>
Perhaps the most important GEM function is providing a command
execution interface to clients. Client programs construct command
buffers containing references to previously allocated memory objects
and submit them to GEM. At that point, GEM will take care to bind
buffers containing references to previously allocated memory objects,
and then submit them to GEM. At that point, GEM takes care to bind
all the objects into the GTT, execute the buffer, and provide
necessary synchronization between clients accessing the same buffers.
This often involves evicting some objects from the GTT and re-binding
others (a fairly expensive operation), and providing relocation
support which hides fixed GTT offsets from clients. Clients must
take care not to submit command buffers that reference more objects
than can fit in the GTT or GEM will reject them and no rendering
than can fit in the GTT; otherwise, GEM will reject them and no rendering
will occur. Similarly, if several objects in the buffer require
fence registers to be allocated for correct rendering (e.g. 2D blits
on pre-965 chips), care must be taken not to require more fence
@ -729,7 +759,7 @@ void intel_crt_init(struct drm_device *dev)
<title>Output management</title>
<para>
At the core of the DRM output management code is a set of
structures representing CRTCs, encoders and connectors.
structures representing CRTCs, encoders, and connectors.
</para>
<para>
A CRTC is an abstraction representing a part of the chip that
@ -765,21 +795,19 @@ void intel_crt_init(struct drm_device *dev)
<sect1>
<title>Framebuffer management</title>
<para>
In order to set a mode on a given CRTC, encoder and connector
configuration, clients need to provide a framebuffer object which
will provide a source of pixels for the CRTC to deliver to the encoder(s)
and ultimately the connector(s) in the configuration. A framebuffer
is fundamentally a driver specific memory object, made into an opaque
handle by the DRM addfb function. Once an fb has been created this
way it can be passed to the KMS mode setting routines for use in
a configuration.
Clients need to provide a framebuffer object which provides a source
of pixels for a CRTC to deliver to the encoder(s) and ultimately the
connector(s). A framebuffer is fundamentally a driver-specific memory
object, made into an opaque handle by the DRM's addfb() function.
Once a framebuffer has been created this way, it may be passed to the
KMS mode setting routines for use in a completed configuration.
</para>
</sect1>
<sect1>
<title>Command submission &amp; fencing</title>
<para>
This should cover a few device specific command submission
This should cover a few device-specific command submission
implementations.
</para>
</sect1>
@ -789,7 +817,7 @@ void intel_crt_init(struct drm_device *dev)
<para>
The DRM core provides some suspend/resume code, but drivers
wanting full suspend/resume support should provide save() and
restore() functions. These will be called at suspend,
restore() functions. These are called at suspend,
hibernate, or resume time, and should perform any state save or
restore required by your device across suspend or hibernate
states.
@ -812,8 +840,8 @@ void intel_crt_init(struct drm_device *dev)
<para>
The DRM core exports several interfaces to applications,
generally intended to be used through corresponding libdrm
wrapper functions. In addition, drivers export device specific
interfaces for use by userspace drivers &amp; device aware
wrapper functions. In addition, drivers export device-specific
interfaces for use by userspace drivers &amp; device-aware
applications through ioctls and sysfs files.
</para>
<para>
@ -822,8 +850,8 @@ void intel_crt_init(struct drm_device *dev)
management, memory management, and output management.
</para>
<para>
Cover generic ioctls and sysfs layout here. Only need high
level info, since man pages will cover the rest.
Cover generic ioctls and sysfs layout here. We only need high-level
info, since man pages should cover the rest.
</para>
</chapter>

4
drivers/gpu/drm/i915/i915_drv.c
Просмотреть файл

@ -789,8 +789,8 @@ static struct vm_operations_struct i915_gem_vm_ops = {
};
static struct drm_driver driver = {
/* don't use mtrr's here, the Xserver or user space app should
* deal with them for intel hardware.
/* Don't use MTRRs here; the Xserver or userspace app should
* deal with them for Intel hardware.
*/
.driver_features =
DRIVER_USE_AGP | DRIVER_REQUIRE_AGP | /* DRIVER_USE_MTRR |*/