diff options
| author | Chris Wilson <chris@chris-wilson.co.uk> | 2017-10-27 10:43:11 +0100 |
|---|---|---|
| committer | Chris Wilson <chris@chris-wilson.co.uk> | 2017-10-27 12:09:29 +0100 |
| commit | 11caf5517c2c9eebd435c60e9343a3784d74e9a1 (patch) | |
| tree | 2528a96186675d35d2a3fdba9f5195beb18a44c0 | |
| parent | e6ed2a1b99051bc04abcc2daed3972efada0b7a9 (diff) | |
drm/i915: Empty the ring before disabling
An interesting snippet from Sandybridge's prm:
"Although a Ring Buffer can be enabled in the non-empty state, it must
not be disabled unless it is empty. Attempting to disable a Ring Buffer
in the non-empty state is UNDEFINED."
Let's avoid the undefined behaviour as we disable the rings prior to
reset and resume.
v2: Tell HEAD to catch up to TAIL (empty ring) first, then reset both to
0 (supposedly while stopped).
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171027094311.30380-1-chris@chris-wilson.co.uk
| -rw-r--r-- | drivers/gpu/drm/i915/intel_ringbuffer.c | 6 | ||||
| -rw-r--r-- | drivers/gpu/drm/i915/intel_uncore.c | 6 |
2 files changed, 10 insertions, 2 deletions
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c index 05e01446b00b..47fadf8da84e 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -480,10 +480,14 @@ static bool stop_ring(struct intel_engine_cs *engine) } } - I915_WRITE_CTL(engine, 0); + I915_WRITE_HEAD(engine, I915_READ_TAIL(engine)); + I915_WRITE_HEAD(engine, 0); I915_WRITE_TAIL(engine, 0); + /* The ring must be empty before it is disabled */ + I915_WRITE_CTL(engine, 0); + return (I915_READ_HEAD(engine) & HEAD_ADDR) == 0; } diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c index 20e3c65c0999..96ee6b2754be 100644 --- a/drivers/gpu/drm/i915/intel_uncore.c +++ b/drivers/gpu/drm/i915/intel_uncore.c @@ -1387,10 +1387,14 @@ static void gen3_stop_engine(struct intel_engine_cs *engine) DRM_DEBUG_DRIVER("%s: timed out on STOP_RING\n", engine->name); - I915_WRITE_FW(RING_CTL(base), 0); + I915_WRITE_FW(RING_HEAD(base), I915_READ_FW(RING_TAIL(base))); + I915_WRITE_FW(RING_HEAD(base), 0); I915_WRITE_FW(RING_TAIL(base), 0); + /* The ring must be empty before it is disabled */ + I915_WRITE_FW(RING_CTL(base), 0); + /* Check acts as a post */ if (I915_READ_FW(RING_HEAD(base)) != 0) DRM_DEBUG_DRIVER("%s: ring head not parked\n", |