diff options
| author | Jiri Kosina <jkosina@suse.cz> | 2014-08-07 16:29:53 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-10-05 14:52:09 -0700 |
| commit | b4216116fd15a2609a39c8b40d46fb372c493439 (patch) | |
| tree | 90ff1efe72c5072552043af2184808f9e07b53c7 | |
| parent | e9c15f9c379c9bc33a412e71f5d99d6bd0b4e758 (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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -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 31b36c5ac894..d488fc71ef49 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -475,6 +475,9 @@ 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 |