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linux/drivers/gpu/drm
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Chris Wilson bcf9dcc1e6 drm/i915: Workaround hang with BSD and forcewake on SandyBridge 
For reasons that are not apparent to anybody, 990bbdadab (drm/i915:
Group the GT routines together in both code and vtable) breaks the use
of the BitStream Decoder ring on SandyBridge. The active ingredient of
that patch is the conversion from a udelay(10) to a udelay(1) in the
busy-wait loop of waiting for the forcewake acknowledge. If we restore
that udelay(10) or insert another udelay(1) afterwards (or any wait
longer than 250ns) everything works again. An alternative is also to
remove any delay from the busy-wait loop.

Given that in the atomic sections we want to complete the wait as quick
as possible to avoid blocking the CPU for too long, it makes sense to
remove the delay altogether and simply spin on the exit condition until
it completes. So we replace the udelay(1) with cpu_relax().

Papers over regression from

commit 990bbdadab
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Mon Jul 2 11:51:02 2012 -0300

    drm/i915: Group the GT routines together in both code and vtable

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=51738
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2012-08-06 10:43:29 +02:00
..
ast drm: Make the .mode_fixup() operations mode argument a const pointer 2012-07-19 21:52:38 -04:00
cirrus drm: Make the .mode_fixup() operations mode argument a const pointer 2012-07-19 21:52:38 -04:00
exynos drm: Make the .mode_fixup() operations mode argument a const pointer 2012-07-19 21:52:38 -04:00
gma500 drm: kill reclaim_buffers callback 2012-07-19 22:50:28 -04:00
i2c drm: Make the .mode_fixup() operations mode argument a const pointer 2012-07-19 21:52:38 -04:00
i810 drm: kill dma queue support 2012-07-19 22:50:55 -04:00
i915 drm/i915: Workaround hang with BSD and forcewake on SandyBridge 2012-08-06 10:43:29 +02:00
mga drm: kill reclaim_buffers callback 2012-07-19 22:50:28 -04:00
mgag200 drm/mgag200: fix null pointer dereference 2012-07-19 22:05:25 -04:00
nouveau drm: kill reclaim_buffers callback 2012-07-19 22:50:28 -04:00
r128 drm: kill reclaim_buffers callback 2012-07-19 22:50:28 -04:00
radeon drm: kill reclaim_buffers callback 2012-07-19 22:50:28 -04:00
savage drm/savage: clean up reclaim_buffers 2012-07-19 22:50:16 -04:00
sis drm/sis: fixup sis_mm ioctl structs 2012-07-19 22:51:58 -04:00
tdfx drm: kill reclaim_buffers callback 2012-07-19 22:50:28 -04:00
ttm drm/ttm: Fix buffer object metadata accounting regression v2 2012-06-12 15:57:47 +01:00
udl drm/udl: port over blanking code from udlfb. 2012-07-19 22:30:41 -04:00
via drm/via: clean up reclaim_buffers 2012-07-19 22:48:28 -04:00
vmwgfx drm: kill reclaim_buffers_locked 2012-07-19 22:49:58 -04:00
ati_pcigart.c
drm_agpsupport.c
drm_auth.c
drm_buffer.c
drm_bufs.c drm: kill dma queue support 2012-07-19 22:50:55 -04:00
drm_cache.c Merge branch 'drm-intel-next' of git://people.freedesktop.org/~danvet/drm-intel into drm-core-next 2012-04-12 10:27:01 +01:00
drm_context.c drm: Unify and fix idr error handling 2012-04-24 09:50:20 +01:00
drm_crtc_helper.c drm: Don't initialize local ret variable when not needed 2012-05-22 10:32:58 +01:00
drm_crtc.c drm: Use stdint types for consistency 2012-05-29 11:07:09 +01:00
drm_debugfs.c drm: kill dma queue support 2012-07-19 22:50:55 -04:00
drm_dma.c drm: kill dma queue support 2012-07-19 22:50:55 -04:00
drm_dp_i2c_helper.c
drm_drv.c drm: kill dma queue support 2012-07-19 22:50:55 -04:00
drm_edid_load.c drm: Don't initialize local ret variable when not needed 2012-05-22 10:32:58 +01:00
drm_edid_modes.h drm: replace open-coded ARRAY_SIZE with macro 2012-04-20 13:12:16 +01:00
drm_edid.c drm/edid: don't return stack garbage from supports_rb 2012-06-21 09:34:13 +01:00
drm_encoder_slave.c
drm_fb_helper.c drm/fb helper: don't call drm_crtc_helper_set_config 2012-07-19 21:24:32 -04:00
drm_fops.c drm: unconditionally clean up dma buffers of closing clients 2012-07-19 22:51:04 -04:00
drm_gem.c drm: Add colouring to the range allocator 2012-07-16 05:59:37 +10:00
drm_global.c
drm_hashtab.c
drm_info.c drm: kill dma queue support 2012-07-19 22:50:55 -04:00
drm_ioc32.c
drm_ioctl.c drm/prime: expose capability flags for userspace. 2012-05-18 11:12:16 +01:00
drm_irq.c drm: Disallow DRM_IOCTL_MODESET_CTL for KMS drivers 2012-07-18 06:05:48 +10:00
drm_lock.c drm: ditch strange DRIVER_DMA_QUEUE only error bail-out 2012-07-19 22:50:47 -04:00
drm_memory.c drm: remove unused code 2012-02-29 10:18:29 +00:00
drm_mm.c drm: Add colouring to the range allocator 2012-07-16 05:59:37 +10:00
drm_modes.c drm: Add drm_mode_copy() 2012-03-15 09:52:51 +00:00
drm_pci.c drm/pci: add support for getting the supported link bw. 2012-07-19 22:29:25 -04:00
drm_platform.c drm: cope with platformdev->id == -1 2012-03-07 14:03:40 +00:00
drm_prime.c drm/prime: add exported buffers to current fprivs imported buffer list (v2) 2012-05-23 10:46:03 +01:00
drm_proc.c drm: kill dma queue support 2012-07-19 22:50:55 -04:00
drm_scatter.c
drm_stub.c drm: Don't initialize local ret variable when not needed 2012-05-22 10:32:58 +01:00
drm_sysfs.c drm: fail gracefully when proc isn't setup. 2012-07-16 05:57:03 +10:00
drm_trace_points.c
drm_trace.h
drm_usb.c drm/usb: fix module license on drm/usb layer. 2012-04-19 09:33:32 +01:00
drm_vm.c drm: pass dev to drm_vm_{open,close}_locked() 2012-05-11 17:37:46 +01:00
Kconfig drm/kms: driver for virtual cirrus under qemu 2012-05-17 11:02:24 +01:00
Makefile drm/kms: driver for virtual cirrus under qemu 2012-05-17 11:02:24 +01:00
README.drm

README.drm 

************************************************************
* For the very latest on DRI development, please see:      *
*     http://dri.freedesktop.org/                          *
************************************************************

The Direct Rendering Manager (drm) is a device-independent kernel-level
device driver that provides support for the XFree86 Direct Rendering
Infrastructure (DRI).

The DRM supports the Direct Rendering Infrastructure (DRI) in four major
ways:

    1. The DRM provides synchronized access to the graphics hardware via
       the use of an optimized two-tiered lock.

    2. The DRM enforces the DRI security policy for access to the graphics
       hardware by only allowing authenticated X11 clients access to
       restricted regions of memory.

    3. The DRM provides a generic DMA engine, complete with multiple
       queues and the ability to detect the need for an OpenGL context
       switch.

    4. The DRM is extensible via the use of small device-specific modules
       that rely extensively on the API exported by the DRM module.


Documentation on the DRI is available from:
    http://dri.freedesktop.org/wiki/Documentation
    http://sourceforge.net/project/showfiles.php?group_id=387
    http://dri.sourceforge.net/doc/

For specific information about kernel-level support, see:

    The Direct Rendering Manager, Kernel Support for the Direct Rendering
    Infrastructure
    http://dri.sourceforge.net/doc/drm_low_level.html

    Hardware Locking for the Direct Rendering Infrastructure
    http://dri.sourceforge.net/doc/hardware_locking_low_level.html

    A Security Analysis of the Direct Rendering Infrastructure
    http://dri.sourceforge.net/doc/security_low_level.html