[PATCH v2, 4/4] drm/i915: abolish separate per-engine default_context pointers

[Dave Gordon <david.s.gordon@intel.com>]

Now that we've eliminated a lot of uses of engine::default_context,
we can eliminate the pointer itself.

All the engines share the same default intel_context, so we can just
keep a single reference to it in the dev_priv structure rather than one
in each of the engine[] elements. This make refcounting more sensible
too, as we now have a refcount of one for the one pointer, rather than
a refcount of one but multiple pointers.

From an idea by Chris Wilson.

Signed-off-by: Dave Gordon <david.s.gordon@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h            |  2 ++
 drivers/gpu/drm/i915/i915_gem.c            |  4 ++--
 drivers/gpu/drm/i915/i915_gem_context.c    | 22 ++++++++--------------
 drivers/gpu/drm/i915/i915_gpu_error.c      |  2 +-
 drivers/gpu/drm/i915/i915_guc_submission.c |  6 +++---
 drivers/gpu/drm/i915/intel_lrc.c           | 14 ++++++++------
 drivers/gpu/drm/i915/intel_ringbuffer.h    |  1 -
 7 files changed, 24 insertions(+), 27 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 56d149e..8ed89a1f 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1946,6 +1946,8 @@ struct drm_i915_private {
 		void (*stop_ring)(struct intel_engine_cs *ring);
 	} gt;
 
+	struct intel_context *kernel_context;
+
 	bool edp_low_vswing;
 
 	/* perform PHY state sanity checks? */
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 927ebc8..01b1eea 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2763,7 +2763,7 @@ i915_gem_request_alloc_anon(struct intel_engine_cs *ring)
 	struct drm_i915_gem_request *req;
 	int err;
 
-	err = i915_gem_request_alloc(ring, ring->default_context, &req);
+	err = i915_gem_request_alloc(ring, dev_priv->kernel_context, &req);
 	return err ? ERR_PTR(err) : req;
 }
 
@@ -4850,7 +4850,7 @@ i915_gem_init_hw(struct drm_device *dev)
 	 */
 	init_unused_rings(dev);
 
-	BUG_ON(!dev_priv->ring[RCS].default_context);
+	BUG_ON(!dev_priv->kernel_context);
 
 	ret = i915_ppgtt_init_hw(dev);
 	if (ret) {
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 43437af..c0efec3 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -355,11 +355,10 @@ int i915_gem_context_init(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_context *ctx;
-	int i;
 
 	/* Init should only be called once per module load. Eventually the
 	 * restriction on the context_disabled check can be loosened. */
-	if (WARN_ON(dev_priv->ring[RCS].default_context))
+	if (WARN_ON(dev_priv->kernel_context))
 		return 0;
 
 	if (intel_vgpu_active(dev) && HAS_LOGICAL_RING_CONTEXTS(dev)) {
@@ -390,12 +389,7 @@ int i915_gem_context_init(struct drm_device *dev)
 		return PTR_ERR(ctx);
 	}
 
-	for (i = 0; i < I915_NUM_RINGS; i++) {
-		struct intel_engine_cs *ring = &dev_priv->ring[i];
-
-		/* NB: RCS will hold a ref for all rings */
-		ring->default_context = ctx;
-	}
+	dev_priv->kernel_context = ctx;
 
 	DRM_DEBUG_DRIVER("%s context support initialized\n",
 			i915.enable_execlists ? "LR" :
@@ -406,7 +400,7 @@ int i915_gem_context_init(struct drm_device *dev)
 void i915_gem_context_fini(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
-	struct intel_context *dctx = dev_priv->ring[RCS].default_context;
+	struct intel_context *dctx = dev_priv->kernel_context;
 	int i;
 
 	if (dctx->legacy_hw_ctx.rcs_state) {
@@ -433,17 +427,17 @@ void i915_gem_context_fini(struct drm_device *dev)
 		i915_gem_object_ggtt_unpin(dctx->legacy_hw_ctx.rcs_state);
 	}
 
-	for (i = 0; i < I915_NUM_RINGS; i++) {
+	for (i = I915_NUM_RINGS; --i >= 0;) {
 		struct intel_engine_cs *ring = &dev_priv->ring[i];
 
-		if (ring->last_context)
+		if (ring->last_context) {
 			i915_gem_context_unreference(ring->last_context);
-
-		ring->default_context = NULL;
-		ring->last_context = NULL;
+			ring->last_context = NULL;
+		}
 	}
 
 	i915_gem_context_unreference(dctx);
+	dev_priv->kernel_context = NULL;
 }
 
 int i915_gem_context_enable(struct drm_i915_gem_request *req)
diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index 06ca408..7eeb244 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -1050,7 +1050,7 @@ static void i915_gem_record_rings(struct drm_device *dev,
 			if (request)
 				rbuf = request->ctx->engine[ring->id].ringbuf;
 			else
-				rbuf = ring->default_context->engine[ring->id].ringbuf;
+				rbuf = dev_priv->kernel_context->engine[ring->id].ringbuf;
 		} else
 			rbuf = ring->buffer;
 
diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
index 9cc3b84..70d0da6 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -863,7 +863,7 @@ int i915_guc_submission_enable(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct intel_guc *guc = &dev_priv->guc;
-	struct intel_context *ctx = dev_priv->ring[RCS].default_context;
+	struct intel_context *ctx = dev_priv->kernel_context;
 	struct i915_guc_client *client;
 
 	/* client for execbuf submission */
@@ -917,7 +917,7 @@ int intel_guc_suspend(struct drm_device *dev)
 	if (!i915.enable_guc_submission)
 		return 0;
 
-	ctx = dev_priv->ring[RCS].default_context;
+	ctx = dev_priv->kernel_context;
 
 	data[0] = HOST2GUC_ACTION_ENTER_S_STATE;
 	/* any value greater than GUC_POWER_D0 */
@@ -943,7 +943,7 @@ int intel_guc_resume(struct drm_device *dev)
 	if (!i915.enable_guc_submission)
 		return 0;
 
-	ctx = dev_priv->ring[RCS].default_context;
+	ctx = dev_priv->kernel_context;
 
 	data[0] = HOST2GUC_ACTION_EXIT_S_STATE;
 	data[1] = GUC_POWER_D0;
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index cf76d28..743ac81 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1471,7 +1471,7 @@ static int gen8_init_common_ring(struct intel_engine_cs *ring)
 	u8 next_context_status_buffer_hw;
 
 	lrc_setup_hardware_status_page(ring,
-				ring->default_context->engine[ring->id].state);
+				dev_priv->kernel_context->engine[ring->id].state);
 
 	I915_WRITE_IMR(ring, ~(ring->irq_enable_mask | ring->irq_keep_mask));
 	I915_WRITE(RING_HWSTAM(ring->mmio_base), 0xffffffff);
@@ -1913,6 +1913,9 @@ void intel_logical_ring_cleanup(struct intel_engine_cs *ring)
 
 static int logical_ring_init(struct drm_device *dev, struct intel_engine_cs *ring)
 {
+	struct drm_i915_private *dev_priv = to_i915(dev);
+	struct intel_context *dctx = dev_priv->kernel_context;
+	int ring_id = ring->id;
 	int ret;
 
 	/* Intentionally left blank. */
@@ -1933,15 +1936,14 @@ static int logical_ring_init(struct drm_device *dev, struct intel_engine_cs *rin
 	if (ret)
 		goto error;
 
-	ret = intel_lr_context_deferred_alloc(ring->default_context, ring);
+	ret = intel_lr_context_deferred_alloc(dctx, ring);
 	if (ret)
 		goto error;
 
 	/* As this is the default context, always pin it */
-	ret = intel_lr_context_do_pin(
-			ring,
-			ring->default_context->engine[ring->id].state,
-			ring->default_context->engine[ring->id].ringbuf);
+	ret = intel_lr_context_do_pin(ring,
+				      dctx->engine[ring_id].state,
+				      dctx->engine[ring_id].ringbuf);
 	if (ret) {
 		DRM_ERROR(
 			"Failed to pin and map ringbuffer %s: %d\n",
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 49574ff..e950f6c 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -305,7 +305,6 @@ struct  intel_engine_cs {
 
 	wait_queue_head_t irq_queue;
 
-	struct intel_context *default_context;
 	struct intel_context *last_context;
 
 	struct intel_ring_hangcheck hangcheck;
-- 
1.9.1

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