[PATCH v4] drm/bridge: sii902x: Fix HDMI detection with DRM_BRIDGE_ATTACH_NO_CONNECTOR

[Devarsh Thakkar <devarsht@ti.com>]

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 <devarsht@ti.com>
---
V4: Shift HDMI detection to atomic_enable() and remove sink_is_hdmi caching
V3: Use drm_edid_connector_update without edid NULL check
V2: Use drm_edid_connector_update to detect HDMI

Link to V3:
https://lore.kernel.org/all/20251007112309.1103811-1-devarsht@ti.com/
Link to V2:
https://lore.kernel.org/all/20251006150714.3144368-1-devarsht@ti.com/
Link to V1:
https://lore.kernel.org/all/20251003143642.4072918-1-devarsht@ti.com/

 drivers/gpu/drm/bridge/sii902x.c | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/bridge/sii902x.c b/drivers/gpu/drm/bridge/sii902x.c
index d537b1d036fb..1f0aba28ad1e 100644
--- a/drivers/gpu/drm/bridge/sii902x.c
+++ b/drivers/gpu/drm/bridge/sii902x.c
@@ -179,7 +179,6 @@ struct sii902x {
 	struct drm_connector connector;
 	struct gpio_desc *reset_gpio;
 	struct i2c_mux_core *i2cmux;
-	bool sink_is_hdmi;
 	u32 bus_width;
 
 	/*
@@ -315,8 +314,6 @@ static int sii902x_get_modes(struct drm_connector *connector)
 		drm_edid_free(drm_edid);
 	}
 
-	sii902x->sink_is_hdmi = connector->display_info.is_hdmi;
-
 	return num;
 }
 
@@ -342,9 +339,17 @@ static void sii902x_bridge_atomic_enable(struct drm_bridge *bridge,
 					 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));
@@ -359,16 +364,12 @@ static void sii902x_bridge_mode_set(struct drm_bridge *bridge,
 				    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;
 	buf[2] = drm_mode_vrefresh(adj);
@@ -384,11 +385,6 @@ static void sii902x_bridge_mode_set(struct drm_bridge *bridge,
 
 	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)
 		goto out;
-- 
2.39.1