WaIdleLiteRestore is an execlists-only workaround, and requires the driver to ensure that any context always has HEAD!=TAIL when attempting lite restore. Add two extra MI_NOOP instructions at the end of each request, but keep the requests tail pointing before the MI_NOOPs. We may not need to executed them, and this is why request->tail must be sampled before adding these extra instructions. If we submit a context to the ELSP which has previously been submitted, move the tail pointer past the MI_NOOPs. This ensures HEAD!=TAIL. v2: Move overallocation to gen8_emit_request, and added note about sampling request->tail in commit message (Chris). Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Signed-off-by: Thomas Daniel <thomas.daniel@xxxxxxxxx> Signed-off-by: Michel Thierry <michel.thierry@xxxxxxxxx> --- drivers/gpu/drm/i915/i915_gem.c | 15 ++++++++++++++- drivers/gpu/drm/i915/intel_lrc.c | 27 ++++++++++++++++++++++++++- 2 files changed, 40 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index 6dd0d57..dc94984 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2364,14 +2364,27 @@ int __i915_add_request(struct intel_engine_cs *ring, ret = ring->emit_request(ringbuf, request); if (ret) return ret; + + request->tail = intel_ring_get_tail(ringbuf); + + if (IS_GEN8(ring->dev) || IS_GEN9(ring->dev)) { + /* + * Here we add two extra NOOPs as padding to avoid + * lite restore of a context with HEAD==TAIL. + */ + intel_logical_ring_emit(ringbuf, MI_NOOP); + intel_logical_ring_emit(ringbuf, MI_NOOP); + intel_logical_ring_advance(ringbuf); + } } else { ret = ring->add_request(ring); if (ret) return ret; + + request->tail = intel_ring_get_tail(ringbuf); } request->head = request_start; - request->tail = intel_ring_get_tail(ringbuf); /* Whilst this request exists, batch_obj will be on the * active_list, and so will hold the active reference. Only when this diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c index 2747b02..1614425 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -427,6 +427,26 @@ static void execlists_context_unqueue(struct intel_engine_cs *ring) } } + if (IS_GEN8(ring->dev) || IS_GEN9(ring->dev)) { + /* + * WaIdleLiteRestore: make sure we never cause a lite + * restore with HEAD==TAIL + */ + if (req0 && req0->elsp_submitted == 1) { + /* + * Consume the buffer NOOPs to ensure HEAD != TAIL when + * submitting. elsp_submitted can only be >1 after + * reset, in which case we don't need the workaround as + * a lite restore will not occur. + */ + struct intel_ringbuffer *ringbuf; + + ringbuf = req0->ctx->engine[ring->id].ringbuf; + req0->tail += 8; + req0->tail &= ringbuf->size - 1; + } + } + WARN_ON(req1 && req1->elsp_submitted); execlists_submit_contexts(ring, req0->ctx, req0->tail, @@ -1272,7 +1292,12 @@ static int gen8_emit_request(struct intel_ringbuffer *ringbuf, u32 cmd; int ret; - ret = intel_logical_ring_begin(ringbuf, request->ctx, 6); + /* + * Reserve space for 2 NOOPs at the end of each request to be + * used as a workaround for not being allowed to do lite + * restore with HEAD==TAIL. + */ + ret = intel_logical_ring_begin(ringbuf, request->ctx, 8); if (ret) return ret; -- 2.1.1 _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx