drm/i915: Rebind bo if currently bound with incorrect alignment.

commit ac0c6b5a upstream.

Whilst pinning the buffer, check that that its current alignment
matches the requested alignment. If it does not, rebind.

This should clear up any final render errors whilst resuming,
for reference:

  Bug 27070 - [i915] Page table errors with empty ringbuffer
  https://bugs.freedesktop.org/show_bug.cgi?id=27070

  Bug 15502 -  render error detected, EIR: 0x00000010
  https://bugzilla.kernel.org/show_bug.cgi?id=15502

  Bug 13844 -  i915 error: "render error detected"
  https://bugzilla.kernel.org/show_bug.cgi?id=13844Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/gpu/drm/i915/i915_gem.c

@@ -4239,6 +4239,17 @@ i915_gem_object_pin(struct drm_gem_object *obj, uint32_t alignment)
 	int ret;
 
 	i915_verify_inactive(dev, __FILE__, __LINE__);
+
+	if (obj_priv->gtt_space != NULL) {
+		if (alignment == 0)
+			alignment = i915_gem_get_gtt_alignment(obj);
+		if (obj_priv->gtt_offset & (alignment - 1)) {
+			ret = i915_gem_object_unbind(obj);
+			if (ret)
+				return ret;
+		}
+	}
+
 	if (obj_priv->gtt_space == NULL) {
 		ret = i915_gem_object_bind_to_gtt(obj, alignment);
 		if (ret)