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drm/i915: enable low power render writes on GEN3 hardware.

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A lot of 945GMs have had stability issues for a long time, this manifested as X hangs, blitter engine hangs, and lots of crashes.

one such report is at:
https://bugs.freedesktop.org/show_bug.cgi?id=20560

along with numerous distro bugzillas.

This only took a week of digging and hair ripping to figure out.

Tracked down and tested on a 945GM Lenovo T60,
previously running
x11perf -copypixwin500
or
x11perf -copywinpix500
repeatedly would cause the GPU to wedge within 4 or 5 tries, with random busy bits set.

After this patch no hangs were observed.

cc: stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>
This commit is contained in:
Dave Airlie 2010-07-20 13:15:31 +10:00
parent 45503ded96
commit 944001201c
1 changed files with 10 additions and 0 deletions
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10
drivers/gpu/drm/i915/i915_gem.c
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@ -4741,6 +4741,16 @@ i915_gem_load(struct drm_device *dev)
list_add(&dev_priv->mm.shrink_list, &shrink_list);
spin_unlock(&shrink_list_lock);
/* On GEN3 we really need to make sure the ARB C3 LP bit is set */
if (IS_GEN3(dev)) {
u32 tmp = I915_READ(MI_ARB_STATE);
if (!(tmp & MI_ARB_C3_LP_WRITE_ENABLE)) {
/* arb state is a masked write, so set bit + bit in mask */
tmp = MI_ARB_C3_LP_WRITE_ENABLE | (MI_ARB_C3_LP_WRITE_ENABLE << MI_ARB_MASK_SHIFT);
I915_WRITE(MI_ARB_STATE, tmp);
}
}
/* Old X drivers will take 0-2 for front, back, depth buffers */
if (!drm_core_check_feature(dev, DRIVER_MODESET))
dev_priv->fence_reg_start = 3;