[Intel-gfx] [PATCH 18/49] drm/i915/bdw: Allocate ringbuffer for LR contexts

[oscar.mateo at intel.com]

From: Ben Widawsky <benjamin.widawsky at intel.com>

With our setup in previous patches, we've allocated one default context
per ring. Now, each of those contexts holds a pointer to the default
ringbuffers and makes its own allocation of the backing objects.

To reiterate the TODO in the patch: the ringbuffer objects are in the
CPU mappable region. This will likely need to change at some point.

Signed-off-by: Ben Widawsky <ben at bwidawsk.net>

v2: Place a ringbuffer pointer inside the context that, in the global
default context, just points to the engine's default ringbuffer. Update
the ringbuffer backing object early instead of waiting for the alloc &
destroy ringbuffer calls during ring initialization.

Signed-off-by: Oscar Mateo <oscar.mateo at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h         |  4 ++
 drivers/gpu/drm/i915/i915_lrc.c         | 65 +++++++++++++++++++++++++++++++--
 drivers/gpu/drm/i915/intel_ringbuffer.c |  8 ++++
 3 files changed, 73 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index ff6a33c..3a36e28 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -597,6 +597,7 @@ struct i915_hw_context {
 	struct drm_i915_file_private *file_priv;
 	struct intel_engine *last_ring;
 	struct drm_i915_gem_object *obj;
+	struct intel_ringbuffer *ringbuf;
 	struct i915_ctx_hang_stats hang_stats;
 	struct i915_address_space *vm;
 
@@ -2317,6 +2318,9 @@ int i915_gem_context_destroy_ioctl(struct drm_device *dev, void *data,
 /* i915_lrc.c */
 int gen8_gem_context_init(struct drm_device *dev);
 void gen8_gem_context_fini(struct drm_device *dev);
+struct i915_hw_context *gen8_gem_create_context(struct drm_device *dev,
+			struct intel_engine *ring,
+			struct drm_i915_file_private *file_priv, bool create_vm);
 
 /* i915_gem_evict.c */
 int __must_check i915_gem_evict_something(struct drm_device *dev,
diff --git a/drivers/gpu/drm/i915/i915_lrc.c b/drivers/gpu/drm/i915/i915_lrc.c
index 10e6dbc..40dfa95 100644
--- a/drivers/gpu/drm/i915/i915_lrc.c
+++ b/drivers/gpu/drm/i915/i915_lrc.c
@@ -43,6 +43,56 @@
 
 #define GEN8_LR_CONTEXT_SIZE (21 * PAGE_SIZE)
 
+struct i915_hw_context *
+gen8_gem_create_context(struct drm_device *dev,
+			struct intel_engine *ring,
+			struct drm_i915_file_private *file_priv,
+			bool create_vm)
+{
+	struct i915_hw_context *ctx = NULL;
+	struct drm_i915_gem_object *ring_obj = NULL;
+	int ret;
+
+	ctx = i915_gem_create_context(dev, file_priv, create_vm);
+	if (IS_ERR_OR_NULL(ctx))
+		return ctx;
+
+	ring_obj = i915_gem_alloc_object(dev, 32 * PAGE_SIZE);
+	if (!ring_obj) {
+		i915_gem_object_ggtt_unpin(ctx->obj);
+		i915_gem_context_unreference(ctx);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	/* TODO: For now we put this in the mappable region so that we can reuse
+	 * the existing ringbuffer code which ioremaps it. When we start
+	 * creating many contexts, this will no longer work and we must switch
+	 * to a kmapish interface.
+	 */
+	ret = i915_gem_obj_ggtt_pin(ring_obj, PAGE_SIZE, PIN_MAPPABLE);
+	if (ret) {
+		drm_gem_object_unreference(&ring_obj->base);
+		i915_gem_object_ggtt_unpin(ctx->obj);
+		i915_gem_context_unreference(ctx);
+		return ERR_PTR(ret);
+	}
+
+	/* Failure at this point is almost impossible */
+	ret = i915_gem_object_set_to_gtt_domain(ring_obj, true);
+	if (ret) {
+		i915_gem_object_ggtt_unpin(ring_obj);
+		drm_gem_object_unreference(&ring_obj->base);
+		i915_gem_object_ggtt_unpin(ctx->obj);
+		i915_gem_context_unreference(ctx);
+		return ERR_PTR(ret);
+	}
+
+	ctx->ringbuf = &ring->default_ringbuf;
+	ctx->ringbuf->obj = ring_obj;
+
+	return ctx;
+}
+
 void gen8_gem_context_fini(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
@@ -50,9 +100,16 @@ void gen8_gem_context_fini(struct drm_device *dev)
 	int unused;
 
 	for_each_ring(ring, dev_priv, unused) {
-		if (ring->default_context) {
-			i915_gem_object_ggtt_unpin(ring->default_context->obj);
-			i915_gem_context_unreference(ring->default_context);
+		struct i915_hw_context *ctx = ring->default_context;
+		if (ctx) {
+			struct drm_i915_gem_object *ring_obj = ctx->ringbuf->obj;
+			if (ring_obj) {
+				i915_gem_object_ggtt_unpin(ring_obj);
+				drm_gem_object_unreference(&ring_obj->base);
+				ctx->ringbuf->obj = NULL;
+			}
+			i915_gem_object_ggtt_unpin(ctx->obj);
+			i915_gem_context_unreference(ctx);
 			ring->default_context = NULL;
 		}
 	}
@@ -69,7 +126,7 @@ int gen8_gem_context_init(struct drm_device *dev)
 	dev_priv->hw_context_size = round_up(GEN8_LR_CONTEXT_SIZE, 4096);
 
 	for_each_ring(ring, dev_priv, ring_id) {
-		ring->default_context = i915_gem_create_context(dev,
+		ring->default_context = gen8_gem_create_context(dev, ring,
 						NULL, (ring_id == RCS));
 		if (IS_ERR_OR_NULL(ring->default_context)) {
 			ret = PTR_ERR(ring->default_context);
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 240e86a..a552c48 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1380,8 +1380,12 @@ static int init_phys_status_page(struct intel_engine *ring)
 
 static void destroy_ring_buffer(struct intel_engine *ring)
 {
+	struct drm_i915_private *dev_priv = ring->dev->dev_private;
 	struct intel_ringbuffer *ringbuf = __get_ringbuf(ring);
 
+	if (dev_priv->lrc_enabled)
+		return;
+
 	i915_gem_object_ggtt_unpin(ringbuf->obj);
 	drm_gem_object_unreference(&ringbuf->obj->base);
 	ringbuf->obj = NULL;
@@ -1390,10 +1394,14 @@ static void destroy_ring_buffer(struct intel_engine *ring)
 static int alloc_ring_buffer(struct intel_engine *ring)
 {
 	struct drm_device *dev = ring->dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct drm_i915_gem_object *obj = NULL;
 	struct intel_ringbuffer *ringbuf = __get_ringbuf(ring);
 	int ret;
 
+	if (dev_priv->lrc_enabled)
+		return 0;
+
 	if (!HAS_LLC(dev))
 		obj = i915_gem_object_create_stolen(dev, ringbuf->size);
 	if (obj == NULL)
-- 
1.9.0