drm/vc4: plane: Ensure fetch_count is sufficient for hw in SAND mode

It has been observed that under some situations the HVS stalls
totally when asked to apply a source crop to a P030/SAND128 image.

Investigation showed that it was always when the start offset
was on component 22 in the range 0-23. Increasing the fetch_count
by 1 under these conditions fixes the problem, so implement that
in the driver.

Signed-off-by: Dave Stevenson <[email protected]>

Author: 6by9

drivers/gpu/drm/vc4/vc4_plane.c

@@ -1943,7 +1943,7 @@ static int vc6_plane_mode_set(struct drm_plane *plane,
 
 		components_per_word = fb->format->format == DRM_FORMAT_P030 ? 24 : 32;
 		starting_offset = src_x % components_per_word;
-		fetch_count = (width + starting_offset + components_per_word - 1) /
+		fetch_count = (width + starting_offset + components_per_word) /
 			components_per_word;
 
 		/* Adjust the base pointer to the first pixel to be scanned