drm/sun4i: backend: Remove ARGB spoofing

We've had some code for quite some time to prevent the alpha bug from
happening on the lowest primary plane. Since we now check for this in our
atomic_check, we can simply remove it.
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/965180afd8169ccaa848f061d16a2c1a9ec4d289.1518802627.git-series.maxime.ripard@bootlin.com

drivers/gpu/drm/sun4i/sun4i_backend.c

@@ -92,13 +92,8 @@ void sun4i_backend_layer_enable(struct sun4i_backend *backend,
 			   SUN4I_BACKEND_MODCTL_LAY_EN(layer), val);
 }
 
-static int sun4i_backend_drm_format_to_layer(struct drm_plane *plane,
-					     u32 format, u32 *mode)
+static int sun4i_backend_drm_format_to_layer(u32 format, u32 *mode)
 {
-	if (plane && (plane->type == DRM_PLANE_TYPE_PRIMARY) &&
-	    (format == DRM_FORMAT_ARGB8888))
-		format = DRM_FORMAT_XRGB8888;
-
 	switch (format) {
 	case DRM_FORMAT_ARGB8888:
 		*mode = SUN4I_BACKEND_LAY_FBFMT_ARGB8888;
@@ -191,8 +186,7 @@ int sun4i_backend_update_layer_formats(struct sun4i_backend *backend,
 	DRM_DEBUG_DRIVER("Switching display backend interlaced mode %s\n",
 			 interlaced ? "on" : "off");
 
-	ret = sun4i_backend_drm_format_to_layer(plane, fb->format->format,
-						&val);
+	ret = sun4i_backend_drm_format_to_layer(fb->format->format, &val);
 	if (ret) {
 		DRM_DEBUG_DRIVER("Invalid format\n");
 		return ret;
@@ -211,7 +205,7 @@ int sun4i_backend_update_layer_frontend(struct sun4i_backend *backend,
 	u32 val;
 	int ret;
 
-	ret = sun4i_backend_drm_format_to_layer(NULL, fmt, &val);
+	ret = sun4i_backend_drm_format_to_layer(fmt, &val);
 	if (ret) {
 		DRM_DEBUG_DRIVER("Invalid format\n");
 		return ret;