[Intel-gfx] [PATCH 44/49] drm/i915: The argument for postfix is redundant

[Chris Wilson]

We are conservative on the amount of free space available in the ring to
avoid overruning the potential MI_INTERRUPT after the seqno write.
Further undermining the justification for the change was that it was
applied incorrectly.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_drv.h         | 14 ++------------
 drivers/gpu/drm/i915/i915_gem.c         | 11 ++---------
 drivers/gpu/drm/i915/i915_gpu_error.c   |  2 +-
 drivers/gpu/drm/i915/intel_lrc.c        |  6 ++----
 drivers/gpu/drm/i915/intel_ringbuffer.c |  2 +-
 5 files changed, 8 insertions(+), 27 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 0d61215f2817..8d6827347fef 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2055,18 +2055,8 @@ struct drm_i915_gem_request {
 	/** GEM sequence number associated with this request. */
 	uint32_t seqno;
 
-	/** Position in the ringbuffer of the start of the request */
-	u32 head;
-
-	/**
-	 * Position in the ringbuffer of the start of the postfix.
-	 * This is required to calculate the maximum available ringbuffer
-	 * space without overwriting the postfix.
-	 */
-	 u32 postfix;
-
-	/** Position in the ringbuffer of the end of the whole request */
-	u32 tail;
+	/** Position in the ringbuffer of the request */
+	u32 head, tail;
 
 	/**
 	 * Context and ring buffer related to this request
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index abd858701307..5fef69b2ce9f 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1369,7 +1369,7 @@ __i915_gem_request_retire__upto(struct drm_i915_gem_request *rq)
 	if (list_empty(&rq->list))
 		return;
 
-	rq->ringbuf->last_retired_head = rq->postfix;
+	rq->ringbuf->last_retired_head = rq->tail;
 
 	do {
 		struct drm_i915_gem_request *prev =
@@ -2439,13 +2439,6 @@ int __i915_add_request(struct intel_engine_cs *ring,
 			return ret;
 	}
 
-	/* Record the position of the start of the request so that
-	 * should we detect the updated seqno part-way through the
-	 * GPU processing the request, we never over-estimate the
-	 * position of the head.
-	 */
-	request->postfix = intel_ring_get_tail(ringbuf);
-
 	if (i915.enable_execlists) {
 		ret = ring->emit_request(ringbuf, request);
 		if (ret)
@@ -2747,7 +2740,7 @@ i915_gem_retire_requests_ring(struct intel_engine_cs *ring)
 		 * of tail of the request to update the last known position
 		 * of the GPU head.
 		 */
-		request->ringbuf->last_retired_head = request->postfix;
+		request->ringbuf->last_retired_head = request->tail;
 		i915_gem_request_retire(request);
 	}
 
diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index 8832f1b2a495..b7a00e464ba4 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -1072,7 +1072,7 @@ static void i915_gem_record_rings(struct drm_device *dev,
 			erq = &error->ring[i].requests[count++];
 			erq->seqno = request->seqno;
 			erq->jiffies = request->emitted_jiffies;
-			erq->tail = request->postfix;
+			erq->tail = request->tail;
 		}
 	}
 }
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 940dbaece3ae..8fa44c3e8c3c 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -407,7 +407,6 @@ void intel_lrc_irq_handler(struct intel_engine_cs *ring)
 
 static int execlists_context_queue(struct intel_engine_cs *ring,
 				   struct intel_context *to,
-				   u32 tail,
 				   struct drm_i915_gem_request *request)
 {
 	if (WARN_ON(request == NULL))
@@ -419,8 +418,6 @@ static int execlists_context_queue(struct intel_engine_cs *ring,
 	i915_gem_request_reference(request);
 	WARN_ON(to != request->ctx);
 
-	request->tail = tail;
-
 	spin_lock_irq(&ring->execlist_lock);
 
 	list_add_tail(&request->execlist_link, &ring->execlist_queue);
@@ -696,7 +693,8 @@ intel_logical_ring_advance_and_submit(struct intel_ringbuffer *ringbuf,
 	if (intel_ring_stopped(ring))
 		return;
 
-	execlists_context_queue(ring, ctx, ringbuf->tail, request);
+	request->tail = ringbuf->tail;
+	execlists_context_queue(ring, ctx, request);
 }
 
 static int intel_lr_context_pin(struct intel_engine_cs *ring,
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 6003e13e05b6..f44e7be17104 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -2106,7 +2106,7 @@ static int ring_wait_for_space(struct intel_engine_cs *ring, int n)
 		return 0;
 
 	list_for_each_entry(request, &ring->request_list, list) {
-		space = __intel_ring_space(request->postfix, ringbuf->tail,
+		space = __intel_ring_space(request->tail, ringbuf->tail,
 					   ringbuf->size);
 		if (space >= n)
 			break;
-- 
2.1.4