drm/i915: Cache ringbuffer GTT VMA

Purpose is to avoid calling i915_gem_obj_ggtt_offset from the
interrupt context without the big lock held.

v2: Renamed gtt_start to gtt_offset. (Daniel Vetter)
v3: Cache the VMA instead of address. (Chris Wilson)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1452870629-13830-2-git-send-email-tvrtko.ursulin@linux.intel.com

drivers/gpu/drm/i915/intel_lrc.c

@@ -391,7 +391,6 @@ static int execlists_update_context(struct drm_i915_gem_request *rq)
 	struct intel_engine_cs *ring = rq->ring;
 	struct i915_hw_ppgtt *ppgtt = rq->ctx->ppgtt;
 	struct drm_i915_gem_object *ctx_obj = rq->ctx->engine[ring->id].state;
-	struct drm_i915_gem_object *rb_obj = rq->ringbuf->obj;
 	struct page *page;
 	uint32_t *reg_state;
 
@@ -401,7 +400,7 @@ static int execlists_update_context(struct drm_i915_gem_request *rq)
 	reg_state = kmap_atomic(page);
 
 	reg_state[CTX_RING_TAIL+1] = rq->tail;
-	reg_state[CTX_RING_BUFFER_START+1] = i915_gem_obj_ggtt_offset(rb_obj);
+	reg_state[CTX_RING_BUFFER_START+1] = rq->ringbuf->vma->node.start;
 
 	if (ppgtt && !USES_FULL_48BIT_PPGTT(ppgtt->base.dev)) {
 		/* True 32b PPGTT with dynamic page allocation: update PDP

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -1999,6 +1999,7 @@ void intel_unpin_ringbuffer_obj(struct intel_ringbuffer *ringbuf)
 	else
 		iounmap(ringbuf->virtual_start);
 	ringbuf->virtual_start = NULL;
+	ringbuf->vma = NULL;
 	i915_gem_object_ggtt_unpin(ringbuf->obj);
 }
 
@@ -2065,6 +2066,8 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
 		}
 	}
 
+	ringbuf->vma = i915_gem_obj_to_ggtt(obj);
+
 	return 0;
 }
 

drivers/gpu/drm/i915/intel_ringbuffer.h

@@ -99,6 +99,7 @@ struct intel_ring_hangcheck {
 struct intel_ringbuffer {
 	struct drm_i915_gem_object *obj;
 	void __iomem *virtual_start;
+	struct i915_vma *vma;
 
 	struct intel_engine_cs *ring;
 	struct list_head link;