[PATCH 9/9] drm/i915/context: Insert MI_SET_CONTEXT in ringbuffer context switch

[Ben Widawsky <bwidawsk@gmail.com>]

Added ringbuffer code to initiate context switch. The context switch can
fail since intel_ring_begin() can fail, and I am not sure how to handle
that yet. In most cases a context switch failure is pretty much fatal.

Modified the locking on deinit, which had a race (though results were
not fatal, just slower).

Fixed execbuffer to pass default_context when there is no context
specified by userspace.
---
 drivers/gpu/drm/i915/i915_context.c        |   28 ++++++++++++-----
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |   13 +++++--
 drivers/gpu/drm/i915/intel_ringbuffer.c    |   46 ++++++++++++++++++++++++++--
 drivers/gpu/drm/i915/intel_ringbuffer.h    |    2 +-
 4 files changed, 73 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_context.c b/drivers/gpu/drm/i915/i915_context.c
index 4f255fb..6674a9d 100644
--- a/drivers/gpu/drm/i915/i915_context.c
+++ b/drivers/gpu/drm/i915/i915_context.c
@@ -81,7 +81,7 @@ i915_context_validate(struct drm_device *dev, struct drm_file *file,
 	struct drm_gem_object *obj;
 	struct drm_i915_gem_object *obj_priv;
 	struct drm_i915_gem_context *ctx;
-	int i, ret = 0;
+	int i;
 
 	ctx = i915_context_lookup_id(dev, ctx_id);
 	if (ctx == NULL) {
@@ -261,21 +261,32 @@ static void i915_context_hw_init(struct drm_device *dev,
 	mutex_unlock(&dev->struct_mutex);
 }
 
-static void i915_context_hw_deinit(struct drm_device *dev,
+static int i915_context_hw_deinit(struct drm_device *dev,
 				   struct drm_i915_gem_context *ctx,
 				   struct intel_ring_buffer *ring)
 {
+	int ret;
+	struct drm_i915_private *dev_priv = dev->dev_private;
+
 	/* XXX We can prevent restoring contexts, but not saving them
 	 * so if we're going to take away our backing context object
 	 * of the last context, we have to switch now.
 	 */
-	struct drm_i915_private *dev_priv = dev->dev_private;
+	mutex_lock(&dev->struct_mutex);
 	if (ring->last_context == ctx && ctx != dev_priv->default_context) {
-		mutex_lock(&dev->struct_mutex);
-		ring->context_switch(ring, dev_priv->default_context,
-				     I915_CONTEXT_NORMAL_SWITCH);
-		mutex_unlock(&dev->struct_mutex);
+		DRM_DEBUG_DRIVER("Switching to default context\n");
+		ret = ring->context_switch(ring, dev_priv->default_context,
+					   I915_CONTEXT_NORMAL_SWITCH);
+		if (ret) {
+			DRM_ERROR("Couldn't switch back to default context\n");
+			goto out;
+		}
+		ring->last_context = dev_priv->default_context;
 	}
+
+out:
+	mutex_unlock(&dev->struct_mutex);
+	return ret;
 }
 
 static int
@@ -428,7 +439,8 @@ void i915_context_init(struct drm_device *dev)
 		dev_priv->ctx_disable = 1;
 		idr_destroy(&dev_priv->i915_ctx_idr);
 	} else {
-		DRM_DEBUG_DRIVER("Context support enabled\n", ret);
+		DRM_DEBUG_DRIVER("Default context = %p\n",
+		 to_intel_bo(dev_priv->default_context->ctx_obj)->gtt_offset);
 	}
 }
 
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 9d022fb..c1d9a0a 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -990,7 +990,7 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 	struct drm_i915_gem_object *batch_obj;
 	struct drm_clip_rect *cliprects = NULL;
 	struct intel_ring_buffer *ring;
-	struct drm_i915_gem_context *ctx;
+	struct drm_i915_gem_context *ctx = NULL;
 	u32 exec_start, exec_len;
 	u32 seqno;
 	u32 ctx_id;
@@ -1013,7 +1013,9 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 			DRM_DEBUG_DRIVER("Context resubmission required\n");
 			return -EIO;
 		}
-	}
+	} else
+		ctx = dev_priv->default_context;
+
 #if WATCH_EXEC
 	DRM_INFO("buffers_ptr %d buffer_count %d len %08x\n",
 		  (int) args->buffers_ptr, args->buffer_count, args->batch_len);
@@ -1203,8 +1205,11 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 		}
 	}
 
-	if (!dev_priv->ctx_disable)
-		ring->context_switch(ring, ctx, I915_CONTEXT_NORMAL_SWITCH);
+	if (!dev_priv->ctx_disable) {
+		ret = ring->context_switch(ring, ctx, I915_CONTEXT_NORMAL_SWITCH);
+		if (ret)
+			goto err;
+	}
 
 	exec_start = batch_obj->gtt_offset + args->batch_start_offset;
 	exec_len = args->batch_len;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 89adb9d..4381730 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -750,15 +750,55 @@ render_ring_dispatch_execbuffer(struct intel_ring_buffer *ring,
 	return 0;
 }
 
-static void
+static int
 render_ring_ctx_switch(struct intel_ring_buffer *ring,
 		       struct drm_i915_gem_context *ctx,
-		       uint32_t flags)
+		       u32 flags)
 {
+	struct drm_device *dev = ring->dev;
+	struct drm_gem_object *obj;
+	uint32_t ctx_switch_flags;
+	int ret = 0;
+
 	if (ring->last_context == ctx)
-		return;
+		return 0;
+
+	DRM_DEBUG_DRIVER("Context switch to %d\n",
+			 ctx->ctx_id);
 
 	ring->last_context = ctx;
+	obj = ctx->ctx_obj;
+
+	if (flags == I915_CONTEXT_SAVE_ONLY)
+		ctx_switch_flags = MI_RESTORE_INHIBIT;
+	else
+		ctx_switch_flags = 0;
+
+	ret = intel_ring_begin(ring, 4);
+	if (ret)
+		return ret;
+
+	if (IS_IRONLAKE_D(dev) || IS_IRONLAKE_M(dev))
+		intel_ring_emit(ring, MI_SUSPEND_FLUSH | MI_SUSPEND_FLUSH_EN);
+	else
+		intel_ring_emit(ring, MI_NOOP);
+
+	intel_ring_emit(ring, MI_SET_CONTEXT);
+	intel_ring_emit(ring, to_intel_bo(obj)->gtt_offset |
+			MI_MM_SPACE_GTT |
+			MI_SAVE_EXT_STATE_EN |
+			MI_RESTORE_EXT_STATE_EN |
+			ctx_switch_flags);
+
+	if (IS_IRONLAKE_D(dev) || IS_IRONLAKE_M(dev))
+		intel_ring_emit(ring, MI_SUSPEND_FLUSH);
+		/* TODO: we may need a NOOP here */
+	else
+		intel_ring_emit(ring, MI_NOOP);
+
+	intel_ring_advance(ring);
+
+	return 0;
 }
 
 static void cleanup_status_page(struct intel_ring_buffer *ring)
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 61525ba..e8f8b6a 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -80,7 +80,7 @@ struct  intel_ring_buffer {
 					       u32 offset, u32 length);
 	void		(*cleanup)(struct intel_ring_buffer *ring);
 	struct		drm_i915_gem_context *last_context;
-	void		(*context_switch)(struct intel_ring_buffer *ring,
+	int		(*context_switch)(struct intel_ring_buffer *ring,
 					  struct drm_i915_gem_context *ctx,
 					  u32 flags);
 
-- 
1.7.3.4