drm/i915: Remove intel_ring.last_retired_head

Storing the position of the breadcrumb of the last retired request as
a separate last_retired_head is superfluous as we always copy that into
head prior to recalculation of the intel_ring.space.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170321102552.24357-1-chris@chris-wilson.co.uk

6 files changed, 7 insertions, 34 deletions

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 47e707d83c4d..29bf11d8b620 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -1938,9 +1938,8 @@ static int i915_gem_framebuffer_info(struct seq_file *m, void *data)
 
 static void describe_ctx_ring(struct seq_file *m, struct intel_ring *ring)
 {
-        seq_printf(m, " (ringbuffer, space: %d, head: %u, tail: %u, last head: %d)",
-                   ring->space, ring->head, ring->tail,
-                   ring->last_retired_head);
+        seq_printf(m, " (ringbuffer, space: %d, head: %u, tail: %u)",
+                   ring->space, ring->head, ring->tail);
 }
 
 static int i915_context_status(struct seq_file *m, void *unused)
diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index 0e8d1010cecb..dbfa9db2419d 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -295,7 +295,7 @@ static void i915_gem_request_retire(struct drm_i915_gem_request *request)
          * completion order.
          */
         list_del(&request->ring_link);
-        request->ring->last_retired_head = request->postfix;
+        request->ring->head = request->postfix;
         if (!--request->i915->gt.active_requests) {
                 GEM_BUG_ON(!request->i915->gt.awake);
                 mod_delayed_work(request->i915->wq,
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index a88380876ce9..090238eefd49 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1260,7 +1260,6 @@ static void reset_common_ring(struct intel_engine_cs *engine,
         ce->lrc_reg_state[CTX_RING_HEAD+1] = request->postfix;
 
         request->ring->head = request->postfix;
-        request->ring->last_retired_head = -1;
         intel_ring_update_space(request->ring);
 
         /* Catch up with any missed context-switch interrupts */
@@ -2047,7 +2046,6 @@ void intel_lr_context_resume(struct drm_i915_private *dev_priv)
                         i915_gem_object_unpin_map(ce->state->obj);
 
                         ce->ring->head = ce->ring->tail = 0;
-                        ce->ring->last_retired_head = -1;
                         intel_ring_update_space(ce->ring);
                 }
         }
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index d9b8d17c3fc6..0ca5ea7a9407 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -49,13 +49,7 @@ static int __intel_ring_space(int head, int tail, int size)
 
 void intel_ring_update_space(struct intel_ring *ring)
 {
-        if (ring->last_retired_head != -1) {
-                ring->head = ring->last_retired_head;
-                ring->last_retired_head = -1;
-        }
-
-        ring->space = __intel_ring_space(ring->head & HEAD_ADDR,
-                                         ring->tail, ring->size);
+        ring->space = __intel_ring_space(ring->head, ring->tail, ring->size);
 }
 
 static int
@@ -618,12 +612,8 @@ static void reset_ring_common(struct intel_engine_cs *engine,
                 }
 
                 /* If the rq hung, jump to its breadcrumb and skip the batch */
-                if (request->fence.error == -EIO) {
-                        struct intel_ring *ring = request->ring;
-
-                        ring->head = request->postfix;
-                        ring->last_retired_head = -1;
-                }
+                if (request->fence.error == -EIO)
+                        request->ring->head = request->postfix;
         } else {
                 engine->legacy_active_context = NULL;
         }
@@ -1392,7 +1382,6 @@ intel_engine_create_ring(struct intel_engine_cs *engine, int size)
         if (IS_I830(engine->i915) || IS_I845G(engine->i915))
                 ring->effective_size -= 2 * CACHELINE_BYTES;
 
-        ring->last_retired_head = -1;
         intel_ring_update_space(ring);
 
         vma = intel_ring_create_vma(engine->i915, size);
@@ -1571,10 +1560,8 @@ void intel_legacy_submission_resume(struct drm_i915_private *dev_priv)
         struct intel_engine_cs *engine;
         enum intel_engine_id id;
 
-        for_each_engine(engine, dev_priv, id) {
+        for_each_engine(engine, dev_priv, id)
                 engine->buffer->head = engine->buffer->tail;
-                engine->buffer->last_retired_head = -1;
-        }
 }
 
 static int ring_request_alloc(struct drm_i915_gem_request *request)
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 847aea554464..2ecb41788fb6 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -149,16 +149,6 @@ struct intel_ring {
         int space;
         int size;
         int effective_size;
-
-        /** We track the position of the requests in the ring buffer, and
-         * when each is retired we increment last_retired_head as the GPU
-         * must have finished processing the request and so we know we
-         * can advance the ringbuffer up to that position.
-         *
-         * last_retired_head is set to -1 after the value is consumed so
-         * we can detect new retirements.
-         */
-        u32 last_retired_head;
 };
 
 struct i915_gem_context;
diff --git a/drivers/gpu/drm/i915/selftests/mock_engine.c b/drivers/gpu/drm/i915/selftests/mock_engine.c
index 8d5ba037064c..0ad624a1db90 100644
--- a/drivers/gpu/drm/i915/selftests/mock_engine.c
+++ b/drivers/gpu/drm/i915/selftests/mock_engine.c
@@ -118,7 +118,6 @@ static struct intel_ring *mock_ring(struct intel_engine_cs *engine)
         ring->vaddr = (void *)(ring + 1);
 
         INIT_LIST_HEAD(&ring->request_list);
-        ring->last_retired_head = -1;
         intel_ring_update_space(ring);
 
         return ring;