Commit 94400120 authored by Dave Airlie's avatar Dave Airlie
Browse files

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

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:

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
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.

Signed-off-by: default avatarDave Airlie <>
parent 45503ded
......@@ -4741,6 +4741,16 @@ i915_gem_load(struct drm_device *dev)
list_add(&dev_priv->mm.shrink_list, &shrink_list);
/* 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 */
/* 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;
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