drm/i915: Fix unfenced alignment on pre-G33 hardware

Align unfenced buffers on older hardware to the power-of-two object
size.  The docs suggest that it should be possible to align only to a
power-of-two tile height, but using the already computed fence size is
easier and always correct. We also have to make sure that we unbind
misaligned buffers upon tiling changes.

In order to prevent a repetition of this bug, we change the interface
to the alignment computation routines to force the caller to provide
the requested alignment and size of the GTT binding rather than assume
the current values on the object.

Reported-and-tested-by: Sitosfe Wheeler <sitsofe@yahoo.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=36326
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@kernel.org
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Keith Packard <keithp@keithp.com>

drivers/gpu/drm/i915/i915_drv.h

@@ -1195,7 +1195,9 @@ void i915_gem_free_all_phys_object(struct drm_device *dev);
 void i915_gem_release(struct drm_device *dev, struct drm_file *file);
 
 uint32_t
-i915_gem_get_unfenced_gtt_alignment(struct drm_i915_gem_object *obj);
+i915_gem_get_unfenced_gtt_alignment(struct drm_device *dev,
+				    uint32_t size,
+				    int tiling_mode);
 
 /* i915_gem_gtt.c */
 void i915_gem_restore_gtt_mappings(struct drm_device *dev);

drivers/gpu/drm/i915/i915_gem.c

@@ -1374,25 +1374,24 @@ i915_gem_free_mmap_offset(struct drm_i915_gem_object *obj)
 }
 
 static uint32_t
-i915_gem_get_gtt_size(struct drm_i915_gem_object *obj)
+i915_gem_get_gtt_size(struct drm_device *dev, uint32_t size, int tiling_mode)
 {
-	struct drm_device *dev = obj->base.dev;
-	uint32_t size;
+	uint32_t gtt_size;
 
 	if (INTEL_INFO(dev)->gen >= 4 ||
-	    obj->tiling_mode == I915_TILING_NONE)
-		return obj->base.size;
+	    tiling_mode == I915_TILING_NONE)
+		return size;
 
 	/* Previous chips need a power-of-two fence region when tiling */
 	if (INTEL_INFO(dev)->gen == 3)
-		size = 1024*1024;
+		gtt_size = 1024*1024;
 	else
-		size = 512*1024;
+		gtt_size = 512*1024;
 
-	while (size < obj->base.size)
-		size <<= 1;
+	while (gtt_size < size)
+		gtt_size <<= 1;
 
-	return size;
+	return gtt_size;
 }
 
 /**
@@ -1403,59 +1402,52 @@ i915_gem_get_gtt_size(struct drm_i915_gem_object *obj)
  * potential fence register mapping.
  */
 static uint32_t
-i915_gem_get_gtt_alignment(struct drm_i915_gem_object *obj)
+i915_gem_get_gtt_alignment(struct drm_device *dev,
+			   uint32_t size,
+			   int tiling_mode)
 {
-	struct drm_device *dev = obj->base.dev;
-
 	/*
 	 * Minimum alignment is 4k (GTT page size), but might be greater
 	 * if a fence register is needed for the object.
 	 */
 	if (INTEL_INFO(dev)->gen >= 4 ||
-	    obj->tiling_mode == I915_TILING_NONE)
+	    tiling_mode == I915_TILING_NONE)
 		return 4096;
 
 	/*
 	 * Previous chips need to be aligned to the size of the smallest
 	 * fence register that can contain the object.
 	 */
-	return i915_gem_get_gtt_size(obj);
+	return i915_gem_get_gtt_size(dev, size, tiling_mode);
 }
 
 /**
  * i915_gem_get_unfenced_gtt_alignment - return required GTT alignment for an
  *					 unfenced object
- * @obj: object to check
+ * @dev: the device
+ * @size: size of the object
+ * @tiling_mode: tiling mode of the object
  *
  * Return the required GTT alignment for an object, only taking into account
  * unfenced tiled surface requirements.
  */
 uint32_t
-i915_gem_get_unfenced_gtt_alignment(struct drm_i915_gem_object *obj)
+i915_gem_get_unfenced_gtt_alignment(struct drm_device *dev,
+				    uint32_t size,
+				    int tiling_mode)
 {
-	struct drm_device *dev = obj->base.dev;
-	int tile_height;
-
 	/*
 	 * Minimum alignment is 4k (GTT page size) for sane hw.
 	 */
 	if (INTEL_INFO(dev)->gen >= 4 || IS_G33(dev) ||
-	    obj->tiling_mode == I915_TILING_NONE)
+	    tiling_mode == I915_TILING_NONE)
 		return 4096;
 
-	/*
-	 * Older chips need unfenced tiled buffers to be aligned to the left
-	 * edge of an even tile row (where tile rows are counted as if the bo is
-	 * placed in a fenced gtt region).
+	/* Previous hardware however needs to be aligned to a power-of-two
+	 * tile height. The simplest method for determining this is to reuse
+	 * the power-of-tile object size.
 	 */
-	if (IS_GEN2(dev))
-		tile_height = 16;
-	else if (obj->tiling_mode == I915_TILING_Y && HAS_128_BYTE_Y_TILING(dev))
-		tile_height = 32;
-	else
-		tile_height = 8;
-
-	return tile_height * obj->stride * 2;
+	return i915_gem_get_gtt_size(dev, size, tiling_mode);
 }
 
 int
@@ -2744,9 +2736,16 @@ i915_gem_object_bind_to_gtt(struct drm_i915_gem_object *obj,
 		return -EINVAL;
 	}
 
-	fence_size = i915_gem_get_gtt_size(obj);
-	fence_alignment = i915_gem_get_gtt_alignment(obj);
-	unfenced_alignment = i915_gem_get_unfenced_gtt_alignment(obj);
+	fence_size = i915_gem_get_gtt_size(dev,
+					   obj->base.size,
+					   obj->tiling_mode);
+	fence_alignment = i915_gem_get_gtt_alignment(dev,
+						     obj->base.size,
+						     obj->tiling_mode);
+	unfenced_alignment =
+		i915_gem_get_unfenced_gtt_alignment(dev,
+						    obj->base.size,
+						    obj->tiling_mode);
 
 	if (alignment == 0)
 		alignment = map_and_fenceable ? fence_alignment :

drivers/gpu/drm/i915/i915_gem_tiling.c

@@ -348,7 +348,9 @@ i915_gem_set_tiling(struct drm_device *dev, void *data,
 		/* Rebind if we need a change of alignment */
 		if (!obj->map_and_fenceable) {
 			u32 unfenced_alignment =
-				i915_gem_get_unfenced_gtt_alignment(obj);
+				i915_gem_get_unfenced_gtt_alignment(dev,
+								    obj->base.size,
+								    args->tiling_mode);
 			if (obj->gtt_offset & (unfenced_alignment - 1))
 				ret = i915_gem_object_unbind(obj);
 		}