[Intel-gfx] [PATCH] drm/i915/bdw: Render moot context reset and switch with Execlists

[Thomas Daniel]

These two functions make no sense in an Logical Ring Context & Execlists
world.

v2: We got rid of lrc_enabled and centralized everything in the sanitized
i915.enable_execlists instead.

Signed-off-by: Oscar Mateo <oscar.mateo at intel.com>

v3: Rebased.  Corrected a typo in comment for i915_switch_context and
added a comment that it should not be called in execlist mode. Added
WARN_ON if i915_switch_context is called in execlist mode. Moved check
for execlist mode out of i915_switch_context and into callers. Added
comment in context_reset explaining why nothing is done in execlist
mode.

Signed-off-by: Thomas Daniel <thomas.daniel at intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c         |    8 +++++---
 drivers/gpu/drm/i915/i915_gem_context.c |   16 +++++++++++++++-
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index cb9310b..954a5f9 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2981,9 +2981,11 @@ int i915_gpu_idle(struct drm_device *dev)
 
 	/* Flush everything onto the inactive list. */
 	for_each_ring(ring, dev_priv, i) {
-		ret = i915_switch_context(ring, ring->default_context);
-		if (ret)
-			return ret;
+		if (!i915.enable_execlists) {
+			ret = i915_switch_context(ring, ring->default_context);
+			if (ret)
+				return ret;
+		}
 
 		ret = intel_ring_idle(ring);
 		if (ret)
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 0fdb357..3face51 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -289,6 +289,12 @@ void i915_gem_context_reset(struct drm_device *dev)
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int i;
 
+	/* In execlists mode we will unreference the context when the execlist
+	 * queue is cleared and the requests destroyed.
+	 */
+	if (i915.enable_execlists)
+		return;
+
 	for (i = 0; i < I915_NUM_RINGS; i++) {
 		struct intel_engine_cs *ring = &dev_priv->ring[i];
 		struct intel_context *lctx = ring->last_context;
@@ -397,6 +403,9 @@ int i915_gem_context_enable(struct drm_i915_private *dev_priv)
 
 	BUG_ON(!dev_priv->ring[RCS].default_context);
 
+	if (i915.enable_execlists)
+		return 0;
+
 	for_each_ring(ring, dev_priv, i) {
 		ret = i915_switch_context(ring, ring->default_context);
 		if (ret)
@@ -637,14 +646,19 @@ unpin_out:
  *
  * The context life cycle is simple. The context refcount is incremented and
  * decremented by 1 and create and destroy. If the context is in use by the GPU,
- * it will have a refoucnt > 1. This allows us to destroy the context abstract
+ * it will have a refcount > 1. This allows us to destroy the context abstract
  * object while letting the normal object tracking destroy the backing BO.
+ *
+ * This function should not be used in execlists mode.  Instead the context is
+ * switched by writing to the ELSP and requests keep a reference to their
+ * context.
  */
 int i915_switch_context(struct intel_engine_cs *ring,
 			struct intel_context *to)
 {
 	struct drm_i915_private *dev_priv = ring->dev->dev_private;
 
+	WARN_ON(i915.enable_execlists);
 	WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
 
 	if (to->legacy_hw_ctx.rcs_state == NULL) { /* We have the fake context */
-- 
1.7.9.5