drm/i915: Check overlay stride errata for i830 and i845

Apparently i830 and i845 cannot handle any stride that is not a multiple
of 256, unlike their brethren which do support 64 byte aligned strides.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@kernel.org
Signed-off-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/i915/intel_overlay.c

@@ -958,7 +958,7 @@ static int check_overlay_src(struct drm_device *dev,
 	    || rec->src_width < N_HORIZ_Y_TAPS*4)
 		return -EINVAL;
 
-	/* check alingment constrains */
+	/* check alignment constraints */
 	switch (rec->flags & I915_OVERLAY_TYPE_MASK) {
 		case I915_OVERLAY_RGB:
 			/* not implemented */
@@ -990,6 +990,9 @@ static int check_overlay_src(struct drm_device *dev,
 		return -EINVAL;
 
 	/* stride checking */
+	if (IS_I830(dev) || IS_845G(dev))
+		stride_mask = 255;
+	else
 		stride_mask = 63;
 
 	if (rec->stride_Y & stride_mask || rec->stride_UV & stride_mask)