drm/ingenic: Implement proper .atomic_get_input_bus_fmts

The .atomic_get_input_bus_fmts() callback of our top bridge should
return the possible input formats for a given output format. If the
requested output format is not supported, then NULL should be returned,
otherwise the bus format negociation will end with a bus format that the
encoder does not support.
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://patchwork.freedesktop.org/patch/msgid/ab25925723cff2f3e773e7137567ef86fff5fdba.1649330171.git.hns@goldelico.com

drivers/gpu/drm/ingenic/ingenic-drm-drv.c

@@ -833,6 +833,32 @@ static int ingenic_drm_bridge_atomic_check(struct drm_bridge *bridge,
 	}
 }
 
+static u32 *
+ingenic_drm_bridge_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
+					     struct drm_bridge_state *bridge_state,
+					     struct drm_crtc_state *crtc_state,
+					     struct drm_connector_state *conn_state,
+					     u32 output_fmt,
+					     unsigned int *num_input_fmts)
+{
+	switch (output_fmt) {
+	case MEDIA_BUS_FMT_RGB888_1X24:
+	case MEDIA_BUS_FMT_RGB666_1X18:
+	case MEDIA_BUS_FMT_RGB565_1X16:
+	case MEDIA_BUS_FMT_RGB888_3X8:
+	case MEDIA_BUS_FMT_RGB888_3X8_DELTA:
+		break;
+	default:
+		*num_input_fmts = 0;
+		return NULL;
+	}
+
+	return drm_atomic_helper_bridge_propagate_bus_fmt(bridge, bridge_state,
+							  crtc_state, conn_state,
+							  output_fmt,
+							  num_input_fmts);
+}
+
 static irqreturn_t ingenic_drm_irq_handler(int irq, void *arg)
 {
 	struct ingenic_drm *priv = drm_device_get_priv(arg);
@@ -984,7 +1010,7 @@ static const struct drm_bridge_funcs ingenic_drm_bridge_funcs = {
 	.atomic_reset		= drm_atomic_helper_bridge_reset,
 	.atomic_duplicate_state	= drm_atomic_helper_bridge_duplicate_state,
 	.atomic_destroy_state	= drm_atomic_helper_bridge_destroy_state,
-	.atomic_get_input_bus_fmts = drm_atomic_helper_bridge_propagate_bus_fmt,
+	.atomic_get_input_bus_fmts = ingenic_drm_bridge_atomic_get_input_bus_fmts,
 };
 
 static const struct drm_mode_config_funcs ingenic_drm_mode_config_funcs = {