From cddd726447a36857ef6c5a0068a41e2473c0ac9a Mon Sep 17 00:00:00 2001 From: Michel Thierry Date: Wed, 15 Apr 2015 18:11:33 +0100 Subject: [PATCH] drm/i915: Workaround to avoid lite restore with HEAD==TAIL 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 is 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). v3: Remove redundant request->tail assignment in __i915_add_request, in lrc mode this is already set in execlists_context_queue. Do not add wa implementation details inside gem (Chris). v4: Apply the wa whenever the req has been resubmitted and update comment (Chris). Cc: Chris Wilson Signed-off-by: Michel Thierry Reviewed-by: Chris Wilson --- drivers/gpu/drm/i915/i915_gem.c | 3 ++- drivers/gpu/drm/i915/intel_lrc.c | 35 ++++++++++++++++++++++++++++++++++- 2 files changed, 36 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index f7b8766..badccf0 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -2400,10 +2400,11 @@ int __i915_add_request(struct intel_engine_cs *ring, 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 a798d75..732fd63 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -416,6 +416,26 @@ 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) { + /* + * Apply the wa NOOPS to prevent ring:HEAD == req:TAIL + * as we resubmit the request. See gen8_emit_request() + * for where we prepare the padding after the end of the + * request. + */ + 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, @@ -1277,7 +1297,12 @@ 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 (WaIdleLiteRestore). + */ + ret = intel_logical_ring_begin(ringbuf, request->ctx, 8); if (ret) return ret; @@ -1295,6 +1320,14 @@ static int gen8_emit_request(struct intel_ringbuffer *ringbuf, intel_logical_ring_emit(ringbuf, MI_NOOP); intel_logical_ring_advance_and_submit(ringbuf, request->ctx, request); + /* + * 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); + return 0; } -- 1.9.1