drm/bridge: sii902x: Set input bus format based on bus-width

Introduce a bus-width property to define the number of parallel RGB
input pins connected to the transmitter. The input bus formats are updated
accordingly. If the property is not specified, default to 24-bit bus-width.

Signed-off-by: Wadim Egorov <w.egorov@phytec.de>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20241017085556.3045686-3-w.egorov@phytec.de
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20241017085556.3045686-3-w.egorov@phytec.de

drivers/gpu/drm/bridge/sii902x.c

@@ -180,6 +180,8 @@ struct sii902x {
 	struct gpio_desc *reset_gpio;
 	struct i2c_mux_core *i2cmux;
 	bool sink_is_hdmi;
+	u32 bus_width;
+
 	/*
 	 * Mutex protects audio and video functions from interfering
 	 * each other, by keeping their i2c command sequences atomic.
@@ -477,6 +479,8 @@ static u32 *sii902x_bridge_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
 						     u32 output_fmt,
 						     unsigned int *num_input_fmts)
 {
+
+	struct sii902x *sii902x = bridge_to_sii902x(bridge);
 	u32 *input_fmts;
 
 	*num_input_fmts = 0;
@@ -485,7 +489,20 @@ static u32 *sii902x_bridge_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
 	if (!input_fmts)
 		return NULL;
 
-	input_fmts[0] = MEDIA_BUS_FMT_RGB888_1X24;
+	switch (sii902x->bus_width) {
+	case 16:
+		input_fmts[0] = MEDIA_BUS_FMT_RGB565_1X16;
+		break;
+	case 18:
+		input_fmts[0] = MEDIA_BUS_FMT_RGB666_1X18;
+		break;
+	case 24:
+		input_fmts[0] = MEDIA_BUS_FMT_RGB888_1X24;
+		break;
+	default:
+		return NULL;
+	}
+
 	*num_input_fmts = 1;
 
 	return input_fmts;
@@ -1167,6 +1184,11 @@ static int sii902x_probe(struct i2c_client *client)
 		return PTR_ERR(sii902x->reset_gpio);
 	}
 
+	sii902x->bus_width = 24;
+	endpoint = of_graph_get_endpoint_by_regs(dev->of_node, 0, -1);
+	if (endpoint)
+		of_property_read_u32(endpoint, "bus-width", &sii902x->bus_width);
+
 	endpoint = of_graph_get_endpoint_by_regs(dev->of_node, 1, -1);
 	if (endpoint) {
 		struct device_node *remote = of_graph_get_remote_port_parent(endpoint);