drm/bridge: sii902x: Fix HDMI detection with DRM_BRIDGE_ATTACH_NO_CONNECTOR

The sii902x driver was caching HDMI detection state in a sink_is_hdmi field
and checking it in mode_set() to determine whether to set HDMI or DVI
output mode. This approach had two problems:

1. With DRM_BRIDGE_ATTACH_NO_CONNECTOR (used by modern display drivers like
TIDSS), the bridge's get_modes() is never called. Instead, the
drm_bridge_connector helper calls the bridge's edid_read() and updates the
connector itself. This meant sink_is_hdmi was never populated, causing the
driver to default to DVI mode and breaking HDMI audio.

2. The mode_set() callback doesn't receive atomic state or connector
pointer, making it impossible to check connector->display_info.is_hdmi
directly at that point.

Fix this by moving the HDMI vs DVI decision from mode_set() to
atomic_enable(), where we can access the connector via
drm_atomic_get_new_connector_for_encoder(). This works for both connector
models:

- With DRM_BRIDGE_ATTACH_NO_CONNECTOR: Returns the drm_bridge_connector
created by the display driver, which has already been updated by the
helper's call to drm_edid_connector_update()

- Without DRM_BRIDGE_ATTACH_NO_CONNECTOR (legacy): Returns the connector
embedded in sii902x struct, which gets updated by the bridge's own
get_modes()

Fixes: 3de47e1309c2 ("drm/bridge: sii902x: use display info is_hdmi")
Signed-off-by: Devarsh Thakkar <[e-mail]>
Reviewed-by: Tomi Valkeinen <[e-mail]>
Signed-off-by: Neil Armstrong <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

drivers/gpu/drm/bridge/sii902x.c

···
 	struct drm_connector connector;
 	struct gpio_desc *reset_gpio;
 	struct i2c_mux_core *i2cmux;
-	bool sink_is_hdmi;
 	u32 bus_width;
 
 	/*
···
 		drm_edid_free(drm_edid);
 	}
 
-	sii902x->sink_is_hdmi = connector->display_info.is_hdmi;
-
 	return num;
 }
 
···
 					 struct drm_atomic_state *state)
 {
 	struct sii902x *sii902x = bridge_to_sii902x(bridge);
+	struct drm_connector *connector;
+	u8 output_mode = SII902X_SYS_CTRL_OUTPUT_DVI;
+
+	connector = drm_atomic_get_new_connector_for_encoder(state, bridge->encoder);
+	if (connector && connector->display_info.is_hdmi)
+		output_mode = SII902X_SYS_CTRL_OUTPUT_HDMI;
 
 	mutex_lock(&sii902x->mutex);
 
+	regmap_update_bits(sii902x->regmap, SII902X_SYS_CTRL_DATA,
+			   SII902X_SYS_CTRL_OUTPUT_MODE, output_mode);
 	regmap_update_bits(sii902x->regmap, SII902X_PWR_STATE_CTRL,
 			   SII902X_AVI_POWER_STATE_MSK,
 			   SII902X_AVI_POWER_STATE_D(0));
···
 				    const struct drm_display_mode *adj)
 {
 	struct sii902x *sii902x = bridge_to_sii902x(bridge);
-	u8 output_mode = SII902X_SYS_CTRL_OUTPUT_DVI;
 	struct regmap *regmap = sii902x->regmap;
 	u8 buf[HDMI_INFOFRAME_SIZE(AVI)];
 	struct hdmi_avi_infoframe frame;
 	u16 pixel_clock_10kHz = adj->clock / 10;
 	int ret;
-
-	if (sii902x->sink_is_hdmi)
-		output_mode = SII902X_SYS_CTRL_OUTPUT_HDMI;
 
 	buf[0] = pixel_clock_10kHz & 0xff;
 	buf[1] = pixel_clock_10kHz >> 8;
···
 		 SII902X_TPI_AVI_INPUT_COLORSPACE_RGB;
 
 	mutex_lock(&sii902x->mutex);
-
-	ret = regmap_update_bits(sii902x->regmap, SII902X_SYS_CTRL_DATA,
-				 SII902X_SYS_CTRL_OUTPUT_MODE, output_mode);
-	if (ret)
-		goto out;
 
 	ret = regmap_bulk_write(regmap, SII902X_TPI_VIDEO_DATA, buf, 10);
 	if (ret)