[PATCH 03/18] drm/i915: Record the position of the workarounds in the tail of the request

[Chris Wilson <chris@chris-wilson.co.uk>]

Rather than blindly assuming we need to advance the tail for
resubmitting the request via the ELSP, record the position.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
---
 drivers/gpu/drm/i915/i915_gem_request.h | 15 +++++++++------
 drivers/gpu/drm/i915/intel_lrc.c        |  4 ++--
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_request.h b/drivers/gpu/drm/i915/i915_gem_request.h
index 91014de8bfbc..2faa3bb4c39b 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.h
+++ b/drivers/gpu/drm/i915/i915_gem_request.h
@@ -88,20 +88,23 @@ struct drm_i915_gem_request {
 	 */
 	u32 previous_seqno;
 
-	/** Position in the ringbuffer of the start of the request */
+	/** Position in the ring 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.
+	 * Position in the ring of the start of the postfix.
+	 * This is required to calculate the maximum available ring space
+	 * without overwriting the postfix.
 	 */
 	u32 postfix;
 
-	/** Position in the ringbuffer of the end of the whole request */
+	/** Position in the ring of the end of the whole request */
 	u32 tail;
 
-	/** Preallocate space in the ringbuffer for the emitting the request */
+	/** Position in the ring of the end of any workarounds after the tail */
+	u32 wa_tail;
+
+	/** Preallocate space in the ring for the emitting the request */
 	u32 reserved_space;
 
 	/**
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 48248289d88a..45d417d22610 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -482,8 +482,7 @@ static void execlists_unqueue(struct intel_engine_cs *engine)
 		 * resubmit the request. See gen8_emit_request() for where we
 		 * prepare the padding after the end of the request.
 		 */
-		req0->tail += 8;
-		req0->tail &= req0->ring->size - 1;
+		req0->tail = req0->wa_tail;
 	}
 
 	execlists_elsp_submit_contexts(req0, req1);
@@ -711,6 +710,7 @@ intel_logical_ring_advance(struct drm_i915_gem_request *request)
 	intel_ring_emit(ring, MI_NOOP);
 	intel_ring_emit(ring, MI_NOOP);
 	intel_ring_advance(ring);
+	request->wa_tail = ring->tail;
 
 	/* We keep the previous context alive until we retire the following
 	 * request. This ensures that any the context object is still pinned
-- 
2.9.3

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