drm/i915: Consolidate get_fence with pin_fence

Following the pattern now used for obj->mm.pages, use just pin_fence and
unpin_fence to control access to the fence registers. I.e. instead of
calling get_fence(); pin_fence(), we now just need to call pin_fence().
This will make it easier to reduce the locking requirements around
fence registers.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171009084401.29090-2-chris@chris-wilson.co.ukReviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

drivers/gpu/drm/i915/i915_drv.h

@@ -3759,8 +3759,6 @@ i915_vm_to_ppgtt(struct i915_address_space *vm)
 }
 
 /* i915_gem_fence_reg.c */
-int __must_check i915_vma_get_fence(struct i915_vma *vma);
-int __must_check i915_vma_put_fence(struct i915_vma *vma);
 struct drm_i915_fence_reg *
 i915_reserve_fence(struct drm_i915_private *dev_priv);
 void i915_unreserve_fence(struct drm_i915_fence_reg *fence);

drivers/gpu/drm/i915/i915_gem.c

@@ -1910,7 +1910,7 @@ int i915_gem_fault(struct vm_fault *vmf)
 	if (ret)
 		goto err_unpin;
 
-	ret = i915_vma_get_fence(vma);
+	ret = i915_vma_pin_fence(vma);
 	if (ret)
 		goto err_unpin;
 
@@ -1926,6 +1926,7 @@ int i915_gem_fault(struct vm_fault *vmf)
 			       min_t(u64, vma->size, area->vm_end - area->vm_start),
 			       &ggtt->mappable);
 
+	i915_vma_unpin_fence(vma);
 err_unpin:
 	__i915_vma_unpin(vma);
 err_unlock:

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -367,12 +367,12 @@ eb_pin_vma(struct i915_execbuffer *eb,
 		return false;
 
 	if (unlikely(exec_flags & EXEC_OBJECT_NEEDS_FENCE)) {
-		if (unlikely(i915_vma_get_fence(vma))) {
+		if (unlikely(i915_vma_pin_fence(vma))) {
 			i915_vma_unpin(vma);
 			return false;
 		}
 
-		if (i915_vma_pin_fence(vma))
+		if (vma->fence)
 			exec_flags |= __EXEC_OBJECT_HAS_FENCE;
 	}
 
@@ -385,7 +385,7 @@ static inline void __eb_unreserve_vma(struct i915_vma *vma, unsigned int flags)
 	GEM_BUG_ON(!(flags & __EXEC_OBJECT_HAS_PIN));
 
 	if (unlikely(flags & __EXEC_OBJECT_HAS_FENCE))
-		i915_vma_unpin_fence(vma);
+		__i915_vma_unpin_fence(vma);
 
 	__i915_vma_unpin(vma);
 }
@@ -563,13 +563,13 @@ static int eb_reserve_vma(const struct i915_execbuffer *eb,
 	}
 
 	if (unlikely(exec_flags & EXEC_OBJECT_NEEDS_FENCE)) {
-		err = i915_vma_get_fence(vma);
+		err = i915_vma_pin_fence(vma);
 		if (unlikely(err)) {
 			i915_vma_unpin(vma);
 			return err;
 		}
 
-		if (i915_vma_pin_fence(vma))
+		if (vma->fence)
 			exec_flags |= __EXEC_OBJECT_HAS_FENCE;
 	}
 

drivers/gpu/drm/i915/i915_gem_fence_reg.c

@@ -280,8 +280,7 @@ static int fence_update(struct drm_i915_fence_reg *fence,
  *
  * 0 on success, negative error code on failure.
  */
-int
-i915_vma_put_fence(struct i915_vma *vma)
+int i915_vma_put_fence(struct i915_vma *vma)
 {
 	struct drm_i915_fence_reg *fence = vma->fence;
 
@@ -299,6 +298,8 @@ static struct drm_i915_fence_reg *fence_find(struct drm_i915_private *dev_priv)
 	struct drm_i915_fence_reg *fence;
 
 	list_for_each_entry(fence, &dev_priv->mm.fence_list, link) {
+		GEM_BUG_ON(fence->vma && fence->vma->fence != fence);
+
 		if (fence->pin_count)
 			continue;
 
@@ -313,7 +314,7 @@ static struct drm_i915_fence_reg *fence_find(struct drm_i915_private *dev_priv)
 }
 
 /**
- * i915_vma_get_fence - set up fencing for a vma
+ * i915_vma_pin_fence - set up fencing for a vma
  * @vma: vma to map through a fence reg
  *
  * When mapping objects through the GTT, userspace wants to be able to write
@@ -331,10 +332,11 @@ static struct drm_i915_fence_reg *fence_find(struct drm_i915_private *dev_priv)
  * 0 on success, negative error code on failure.
  */
 int
-i915_vma_get_fence(struct i915_vma *vma)
+i915_vma_pin_fence(struct i915_vma *vma)
 {
 	struct drm_i915_fence_reg *fence;
 	struct i915_vma *set = i915_gem_object_is_tiled(vma->obj) ? vma : NULL;
+	int err;
 
 	/* Note that we revoke fences on runtime suspend. Therefore the user
 	 * must keep the device awake whilst using the fence.
@@ -344,6 +346,8 @@ i915_vma_get_fence(struct i915_vma *vma)
 	/* Just update our place in the LRU if our fence is getting reused. */
 	if (vma->fence) {
 		fence = vma->fence;
+		GEM_BUG_ON(fence->vma != vma);
+		fence->pin_count++;
 		if (!fence->dirty) {
 			list_move_tail(&fence->link,
 				       &fence->i915->mm.fence_list);
@@ -353,10 +357,25 @@ i915_vma_get_fence(struct i915_vma *vma)
 		fence = fence_find(vma->vm->i915);
 		if (IS_ERR(fence))
 			return PTR_ERR(fence);
+
+		GEM_BUG_ON(fence->pin_count);
+		fence->pin_count++;
 	} else
 		return 0;
 
-	return fence_update(fence, set);
+	err = fence_update(fence, set);
+	if (err)
+		goto out_unpin;
+
+	GEM_BUG_ON(fence->vma != set);
+	GEM_BUG_ON(vma->fence != (set ? fence : NULL));
+
+	if (set)
+		return 0;
+
+out_unpin:
+	fence->pin_count--;
+	return err;
 }
 
 /**
@@ -429,6 +448,8 @@ void i915_gem_revoke_fences(struct drm_i915_private *dev_priv)
 	for (i = 0; i < dev_priv->num_fence_regs; i++) {
 		struct drm_i915_fence_reg *fence = &dev_priv->fence_regs[i];
 
+		GEM_BUG_ON(fence->vma && fence->vma->fence != fence);
+
 		if (fence->vma)
 			i915_gem_release_mmap(fence->vma->obj);
 	}
@@ -450,6 +471,8 @@ void i915_gem_restore_fences(struct drm_i915_private *dev_priv)
 		struct drm_i915_fence_reg *reg = &dev_priv->fence_regs[i];
 		struct i915_vma *vma = reg->vma;
 
+		GEM_BUG_ON(vma && vma->fence != reg);
+
 		/*
 		 * Commit delayed tiling changes if we have an object still
 		 * attached to the fence, otherwise just clear the fence.

drivers/gpu/drm/i915/i915_vma.c

@@ -309,12 +309,10 @@ void __iomem *i915_vma_pin_iomap(struct i915_vma *vma)
 
 	__i915_vma_pin(vma);
 
-	err = i915_vma_get_fence(vma);
+	err = i915_vma_pin_fence(vma);
 	if (err)
 		goto err_unpin;
 
-	i915_vma_pin_fence(vma);
-
 	return ptr;
 
 err_unpin:

drivers/gpu/drm/i915/i915_vma.h

@@ -345,15 +345,13 @@ static inline struct page *i915_vma_first_page(struct i915_vma *vma)
  *
  * True if the vma has a fence, false otherwise.
  */
-static inline bool
-i915_vma_pin_fence(struct i915_vma *vma)
+int i915_vma_pin_fence(struct i915_vma *vma);
+int __must_check i915_vma_put_fence(struct i915_vma *vma);
+
+static inline void __i915_vma_unpin_fence(struct i915_vma *vma)
 {
-	lockdep_assert_held(&vma->obj->base.dev->struct_mutex);
-	if (vma->fence) {
-		vma->fence->pin_count++;
-		return true;
-	} else
-		return false;
+	GEM_BUG_ON(vma->fence->pin_count <= 0);
+	vma->fence->pin_count--;
 }
 
 /**
@@ -368,10 +366,8 @@ static inline void
 i915_vma_unpin_fence(struct i915_vma *vma)
 {
 	lockdep_assert_held(&vma->obj->base.dev->struct_mutex);
-	if (vma->fence) {
-		GEM_BUG_ON(vma->fence->pin_count <= 0);
-		vma->fence->pin_count--;
-	}
+	if (vma->fence)
+		__i915_vma_unpin_fence(vma);
 }
 
 #endif

drivers/gpu/drm/i915/intel_display.c

@@ -2219,7 +2219,6 @@ intel_pin_and_fence_fb_obj(struct drm_framebuffer *fb, unsigned int rotation)
 		 * something and try to run the system in a "less than optimal"
 		 * mode that matches the user configuration.
 		 */
-		if (i915_vma_get_fence(vma) == 0)
 		i915_vma_pin_fence(vma);
 	}