From 25732821cb965f00475922ca46e84f78e4bada95 Mon Sep 17 00:00:00 2001 From: Ben Widawsky Date: Fri, 24 Jun 2011 14:31:47 -0700 Subject: [PATCH] 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 Signed-off-by: Ben Widawsky Signed-off-by: Keith Packard --- drivers/gpu/drm/i915/i915_drv.c | 3 +++ 1 file changed, 3 insertions(+) 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) } else switch (INTEL_INFO(dev)->gen) { case 6: ret = gen6_do_reset(dev, flags); + /* If reset with a user forcewake, try to restore */ + if (atomic_read(&dev_priv->forcewake_count)) + __gen6_gt_force_wake_get(dev_priv); break; case 5: ret = ironlake_do_reset(dev, flags);