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authorBen Widawsky <ben@bwidawsk.net>2011-06-24 17:31:47 -0400
committerKeith Packard <keithp@keithp.com>2011-06-28 12:44:55 -0400
commit25732821cb965f00475922ca46e84f78e4bada95 (patch)
treee265e7fe4cb531722b2bfe8ddb17e521f6e460b8
parent7c9017e5b77118439952fe8dc22809bae4fae4b6 (diff)
drm/i915: forcewake fix after reset
The failure is as follows: 1. Userspace gets forcewake lock, lock count >=1 2. GPU hang/reset occurs (forcewake bit is reset) 3. count is now incorrect The failure can only occur when using the forcewake userspace lock. This has the unfortunate consequence of messing up the driver as well as userspace, unless userspace closes the debugfs file, the kernel will never end up waking the GT since the refcount will be > 1. The solution is to try to recover the correct forcewake state based on the refcount. There is a period of time where userspace reads/writes may occur after the reset, before the GT has been forcewaked. The interface was never designed to be a perfect solution for userspace reads/writes, and the kernel portion is fixed by this patch. Suggested-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: Ben Widawsky <ben@bwidawsk.net> Signed-off-by: Keith Packard <keithp@keithp.com>
-rw-r--r--drivers/gpu/drm/i915/i915_drv.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 0defd4270594..609358faaa90 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -579,6 +579,9 @@ int i915_reset(struct drm_device *dev, u8 flags)
579 } else switch (INTEL_INFO(dev)->gen) { 579 } else switch (INTEL_INFO(dev)->gen) {
580 case 6: 580 case 6:
581 ret = gen6_do_reset(dev, flags); 581 ret = gen6_do_reset(dev, flags);
582 /* If reset with a user forcewake, try to restore */
583 if (atomic_read(&dev_priv->forcewake_count))
584 __gen6_gt_force_wake_get(dev_priv);
582 break; 585 break;
583 case 5: 586 case 5:
584 ret = ironlake_do_reset(dev, flags); 587 ret = ironlake_do_reset(dev, flags);