diff options
| author | Jiri Kosina <jkosina@suse.cz> | 2014-08-07 16:29:53 +0200 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2014-09-18 16:40:01 +0200 |
| commit | 7b5e127b34724f698d7567b7222f0cbf3624098b (patch) | |
| tree | a7f4a18ae28169703c8c97e614f7f30c85f8eed1 | |
| parent | c030871d73f59332154e3ebb79b986ae97bacd4a (diff) | |
drm/i915: read HEAD register back in init_ring_common() to enforce ordering
commit ece4a17d237a79f63fbfaf3f724a12b6d500555c upstream.
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>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
| -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 7507fe036b6e..1ceb95a3bbe0 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -423,6 +423,9 @@ static int init_ring_common(struct intel_ring_buffer *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 |