drm/i915: Piggy back hangstats off of contexts

To simplify the codepaths somewhat, we can simply always create a
context. Contexts already keep hangstat information. This prevents us
from having to differentiate at other parts in the code.

There is allocation overhead, but it should not be measurable.
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -1757,7 +1757,6 @@ struct drm_i915_file_private {
 	} mm;
 	struct idr context_idr;
 
-	struct i915_ctx_hang_stats hang_stats;
 	struct i915_hw_context *private_default_ctx;
 	atomic_t rps_wait_boost;
 };
@@ -2244,12 +2243,14 @@ int i915_switch_context(struct intel_ring_buffer *ring,
 void i915_gem_context_free(struct kref *ctx_ref);
 static inline void i915_gem_context_reference(struct i915_hw_context *ctx)
 {
-	kref_get(&ctx->ref);
+	if (ctx->obj && HAS_HW_CONTEXTS(ctx->obj->base.dev))
+		kref_get(&ctx->ref);
 }
 
 static inline void i915_gem_context_unreference(struct i915_hw_context *ctx)
 {
-	kref_put(&ctx->ref, i915_gem_context_free);
+	if (ctx->obj && HAS_HW_CONTEXTS(ctx->obj->base.dev))
+		kref_put(&ctx->ref, i915_gem_context_free);
 }
 
 struct i915_ctx_hang_stats * __must_check

drivers/gpu/drm/i915/i915_gem.c

@@ -2323,7 +2323,7 @@ static void i915_set_reset_status(struct intel_ring_buffer *ring,
 	if (request->ctx && request->ctx->id != DEFAULT_CONTEXT_ID)
 		hs = &request->ctx->hang_stats;
 	else if (request->file_priv)
-		hs = &request->file_priv->hang_stats;
+		hs = &request->file_priv->private_default_ctx->hang_stats;
 
 	if (hs) {
 		if (guilty) {

drivers/gpu/drm/i915/i915_gem_context.c

@@ -490,15 +490,8 @@ i915_gem_context_get_hang_stats(struct drm_device *dev,
 				struct drm_file *file,
 				u32 id)
 {
-	struct drm_i915_file_private *file_priv = file->driver_priv;
 	struct i915_hw_context *ctx;
 
-	if (id == DEFAULT_CONTEXT_ID)
-		return &file_priv->hang_stats;
-
-	if (!HAS_HW_CONTEXTS(dev))
-		return ERR_PTR(-ENOENT);
-
 	ctx = i915_gem_context_get(file->driver_priv, id);
 	if (ctx == NULL)
 		return ERR_PTR(-ENOENT);
@@ -509,9 +502,15 @@ i915_gem_context_get_hang_stats(struct drm_device *dev,
 int i915_gem_context_open(struct drm_device *dev, struct drm_file *file)
 {
 	struct drm_i915_file_private *file_priv = file->driver_priv;
+	struct drm_i915_private *dev_priv = dev->dev_private;
 
-	if (!HAS_HW_CONTEXTS(dev))
+	if (!HAS_HW_CONTEXTS(dev)) {
+		/* Cheat for hang stats */
+		file_priv->private_default_ctx =
+			kzalloc(sizeof(struct i915_hw_context), GFP_KERNEL);
+		file_priv->private_default_ctx->vm = &dev_priv->gtt.base;
 		return 0;
+	}
 
 	idr_init(&file_priv->context_idr);
 
@@ -532,8 +531,10 @@ void i915_gem_context_close(struct drm_device *dev, struct drm_file *file)
 {
 	struct drm_i915_file_private *file_priv = file->driver_priv;
 
-	if (!HAS_HW_CONTEXTS(dev))
+	if (!HAS_HW_CONTEXTS(dev)) {
+		kfree(file_priv->private_default_ctx);
 		return;
+	}
 
 	mutex_lock(&dev->struct_mutex);
 	idr_for_each(&file_priv->context_idr, context_idr_cleanup, NULL);
@@ -714,9 +715,6 @@ int i915_switch_context(struct intel_ring_buffer *ring,
 
 	WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
 
-	if (!HAS_HW_CONTEXTS(ring->dev))
-		return 0;
-
 	if (file == NULL)
 		to = ring->default_context;
 	else
@@ -725,6 +723,10 @@ int i915_switch_context(struct intel_ring_buffer *ring,
 	if (to == NULL)
 		return -ENOENT;
 
+	/* We have the fake context, but don't supports switching. */
+	if (!HAS_HW_CONTEXTS(ring->dev))
+		return 0;
+
 	return do_switch(ring, to);
 }