drm/rcar-du: Fix maximum frame buffer pitch computation

The maximum pitch constraint for the hardware is expressed in pixels.
Convert it to bytes to validate frame buffer creation, as frame buffer
pitches are expressed in bytes.

Reported-by: Phil Edworthy <[e-mail]>
Signed-off-by: Laurent Pinchart <[e-mail]>
Signed-off-by: Dave Airlie <[e-mail]>

drivers/gpu/drm/rcar-du/rcar_du_kms.c

···
 {
 	struct rcar_du_device *rcdu = dev->dev_private;
 	const struct rcar_du_format_info *format;
+	unsigned int max_pitch;
 	unsigned int align;
+	unsigned int bpp;
 
 	format = rcar_du_format_info(mode_cmd->pixel_format);
 	if (format == NULL) {
···
 		return ERR_PTR(-EINVAL);
 	}
 
+	/*
+	 * The pitch and alignment constraints are expressed in pixels on the
+	 * hardware side and in bytes in the DRM API.
+	 */
+	bpp = format->planes == 2 ? 1 : format->bpp / 8;
+	max_pitch =  4096 * bpp;
+
 	if (rcar_du_needs(rcdu, RCAR_DU_QUIRK_ALIGN_128B))
 		align = 128;
 	else
-		align = 16 * format->bpp / 8;
+		align = 16 * bpp;
 
 	if (mode_cmd->pitches[0] & (align - 1) ||
-	    mode_cmd->pitches[0] >= 8192) {
+	    mode_cmd->pitches[0] >= max_pitch) {
 		dev_dbg(dev->dev, "invalid pitch value %u\n",
 			mode_cmd->pitches[0]);
 		return ERR_PTR(-EINVAL);