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| author | Jiri Kosina <jkosina@suse.cz> | 2014-08-07 14:29:53 (GMT) |
|---|---|---|
| committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2014-08-08 14:22:18 (GMT) |
| commit | ece4a17d237a79f63fbfaf3f724a12b6d500555c (patch) | |
| tree | 707d9d7bb4a6e11f8c1b3921b656db70f8da20ed /drivers | |
| parent | ed3b6679936801fa2dab47e7a6ef74e383400ed9 (diff) | |
| download | linux-ece4a17d237a79f63fbfaf3f724a12b6d500555c.tar.xz | |
drm/i915: read HEAD register back in init_ring_common() to enforce ordering
Withtout this, ring initialization fails reliabily during resume with
[drm:init_ring_common] *ERROR* render ring initialization failed ctl 0001f001 head ffffff8804 tail 00000000 start 000e4000
This is not a complete fix, but it is verified to make the ring
initialization failures during resume much less likely.
We were not able to root-cause this bug (likely HW-specific to Gen4 chips)
yet. This is therefore used as a ducttape before problem is fully
understood and proper fix created, so that people don't suffer from
completely unusable systems in the meantime.
The discussion and debugging is happening at
https://bugs.freedesktop.org/show_bug.cgi?id=76554
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/gpu/drm/i915/intel_ringbuffer.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c index 05969f0..16371a4 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -532,6 +532,9 @@ static int init_ring_common(struct intel_engine_cs *ring) else ring_setup_phys_status_page(ring); + /* Enforce ordering by reading HEAD register back */ + I915_READ_HEAD(ring); + /* Initialize the ring. This must happen _after_ we've cleared the ring * registers with the above sequence (the readback of the HEAD registers * also enforces ordering), otherwise the hw might lose the new ring |