On 12/04/16 14:51, Michał Winiarski wrote:
We started to use PIPE_CONTROL to write render ring seqno in order to combat seqno write vs interrupt generation problems. This was introduced by commit 7c17d377374d ("drm/i915: Use ordered seqno write interrupt generation on gen8+ execlists").On gen8+ size of PIPE_CONTROL with Post Sync Operation should be 6 dwords. When we're using older 5-dword variant it's possible to observe inconsistent values written by PIPE_CONTROL with Post Sync Operation from user batches, resulting in rendering corruptions. v2: Fix BAT failures v3: Comments on alignment and thrashing high dword of seqno (Chris) v4: Updated commit msg (Mika) Testcase: igt/gem_pipe_control_store_loop/*-qword-write Issue: VIZ-7393 Cc: sta...@vger.kernel.org Cc: Chris Wilson <ch...@chris-wilson.co.uk> Cc: Mika Kuoppala <mika.kuopp...@intel.com> Cc: Abdiel Janulgue <abdiel.janul...@linux.intel.com> Signed-off-by: Michał Winiarski <michal.winiar...@intel.com> --- drivers/gpu/drm/i915/intel_lrc.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c index 0d6dc5e..30abe53 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -1945,15 +1945,18 @@ static int gen8_emit_request_render(struct drm_i915_gem_request *request) struct intel_ringbuffer *ringbuf = request->ringbuf; int ret; - ret = intel_logical_ring_begin(request, 6 + WA_TAIL_DWORDS); + ret = intel_logical_ring_begin(request, 8 + WA_TAIL_DWORDS); if (ret) return ret; + /* We're using qword write, seqno should be aligned to 8 bytes. */ + BUILD_BUG_ON(I915_GEM_HWS_INDEX & 1); + /* w/a for post sync ops following a GPGPU operation we * need a prior CS_STALL, which is emitted by the flush * following the batch. */ - intel_logical_ring_emit(ringbuf, GFX_OP_PIPE_CONTROL(5)); + intel_logical_ring_emit(ringbuf, GFX_OP_PIPE_CONTROL(6)); intel_logical_ring_emit(ringbuf, (PIPE_CONTROL_GLOBAL_GTT_IVB | PIPE_CONTROL_CS_STALL | @@ -1961,7 +1964,10 @@ static int gen8_emit_request_render(struct drm_i915_gem_request *request) intel_logical_ring_emit(ringbuf, hws_seqno_address(request->engine)); intel_logical_ring_emit(ringbuf, 0); intel_logical_ring_emit(ringbuf, i915_gem_request_get_seqno(request)); + /* We're thrashing one dword of HWS. */ + intel_logical_ring_emit(ringbuf, 0); intel_logical_ring_emit(ringbuf, MI_USER_INTERRUPT); + intel_logical_ring_emit(ringbuf, MI_NOOP); return intel_logical_ring_advance_and_submit(request); }
In the scheduler+preemption patches, we actually make use of the fact that we're writing a QWord, so that we can set the completed-seqno and clear the in-progress seqno in one operation (it doesn't actually matter if the h/w turns it into two DWord writes, though).
.Dave. _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
