drm/bridge-connector: implement glue code for HDMI connector

In order to let bridge chains implement HDMI connector infrastructure,
add necessary glue code to the drm_bridge_connector. In case there is a
bridge that sets DRM_BRIDGE_OP_HDMI, drm_bridge_connector will register
itself as a HDMI connector and provide proxy drm_connector_hdmi_funcs
implementation.

Note, to simplify implementation, there can be only one bridge in a
chain that sets DRM_BRIDGE_OP_HDMI. Setting more than one is considered
an error. This limitation can be lifted later, if the need arises.

Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240607-bridge-hdmi-connector-v5-3-ab384e6021af@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

drivers/gpu/drm/drm_bridge_connector.c

@@ -18,6 +18,7 @@
 #include <drm/drm_managed.h>
 #include <drm/drm_modeset_helper_vtables.h>
 #include <drm/drm_probe_helper.h>
+#include <drm/display/drm_hdmi_state_helper.h>
 
 /**
  * DOC: overview
@@ -87,6 +88,13 @@ struct drm_bridge_connector {
 	 * connector modes detection, if any (see &DRM_BRIDGE_OP_MODES).
 	 */
 	struct drm_bridge *bridge_modes;
+	/**
+	 * @bridge_hdmi:
+	 *
+	 * The bridge in the chain that implements necessary support for the
+	 * HDMI connector infrastructure, if any (see &DRM_BRIDGE_OP_HDMI).
+	 */
+	struct drm_bridge *bridge_hdmi;
 };
 
 #define to_drm_bridge_connector(x) \
@@ -287,6 +295,60 @@ static const struct drm_connector_helper_funcs drm_bridge_connector_helper_funcs
 	.disable_hpd = drm_bridge_connector_disable_hpd,
 };
 
+static enum drm_mode_status
+drm_bridge_connector_tmds_char_rate_valid(const struct drm_connector *connector,
+					  const struct drm_display_mode *mode,
+					  unsigned long long tmds_rate)
+{
+	struct drm_bridge_connector *bridge_connector =
+		to_drm_bridge_connector(connector);
+	struct drm_bridge *bridge;
+
+	bridge = bridge_connector->bridge_hdmi;
+	if (!bridge)
+		return MODE_ERROR;
+
+	if (bridge->funcs->hdmi_tmds_char_rate_valid)
+		return bridge->funcs->hdmi_tmds_char_rate_valid(bridge, mode, tmds_rate);
+	else
+		return MODE_OK;
+}
+
+static int drm_bridge_connector_clear_infoframe(struct drm_connector *connector,
+						enum hdmi_infoframe_type type)
+{
+	struct drm_bridge_connector *bridge_connector =
+		to_drm_bridge_connector(connector);
+	struct drm_bridge *bridge;
+
+	bridge = bridge_connector->bridge_hdmi;
+	if (!bridge)
+		return -EINVAL;
+
+	return bridge->funcs->hdmi_clear_infoframe(bridge, type);
+}
+
+static int drm_bridge_connector_write_infoframe(struct drm_connector *connector,
+						enum hdmi_infoframe_type type,
+						const u8 *buffer, size_t len)
+{
+	struct drm_bridge_connector *bridge_connector =
+		to_drm_bridge_connector(connector);
+	struct drm_bridge *bridge;
+
+	bridge = bridge_connector->bridge_hdmi;
+	if (!bridge)
+		return -EINVAL;
+
+	return bridge->funcs->hdmi_write_infoframe(bridge, type, buffer, len);
+}
+
+static const struct drm_connector_hdmi_funcs drm_bridge_connector_hdmi_funcs = {
+	.tmds_char_rate_valid = drm_bridge_connector_tmds_char_rate_valid,
+	.clear_infoframe = drm_bridge_connector_clear_infoframe,
+	.write_infoframe = drm_bridge_connector_write_infoframe,
+};
+
 /* -----------------------------------------------------------------------------
  * Bridge Connector Initialisation
  */
@@ -312,6 +374,8 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
 	struct drm_connector *connector;
 	struct i2c_adapter *ddc = NULL;
 	struct drm_bridge *bridge, *panel_bridge = NULL;
+	unsigned int supported_formats = BIT(HDMI_COLORSPACE_RGB);
+	unsigned int max_bpc = 8;
 	int connector_type;
 	int ret;
 
@@ -348,6 +412,20 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
 			bridge_connector->bridge_detect = bridge;
 		if (bridge->ops & DRM_BRIDGE_OP_MODES)
 			bridge_connector->bridge_modes = bridge;
+		if (bridge->ops & DRM_BRIDGE_OP_HDMI) {
+			if (bridge_connector->bridge_hdmi)
+				return ERR_PTR(-EBUSY);
+			if (!bridge->funcs->hdmi_write_infoframe ||
+			    !bridge->funcs->hdmi_clear_infoframe)
+				return ERR_PTR(-EINVAL);
+
+			bridge_connector->bridge_hdmi = bridge;
+
+			if (bridge->supported_formats)
+				supported_formats = bridge->supported_formats;
+			if (bridge->max_bpc)
+				max_bpc = bridge->max_bpc;
+		}
 
 		if (!drm_bridge_get_next_bridge(bridge))
 			connector_type = bridge->type;
@@ -370,9 +448,19 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
 		return ERR_PTR(-EINVAL);
 	}
 
-	ret = drmm_connector_init(drm, connector,
+	if (bridge_connector->bridge_hdmi)
-				  &drm_bridge_connector_funcs,
+		ret = drmm_connector_hdmi_init(drm, connector,
-				  connector_type, ddc);
+					       bridge_connector->bridge_hdmi->vendor,
+					       bridge_connector->bridge_hdmi->product,
+					       &drm_bridge_connector_funcs,
+					       &drm_bridge_connector_hdmi_funcs,
+					       connector_type, ddc,
+					       supported_formats,
+					       max_bpc);
+	else
+		ret = drmm_connector_init(drm, connector,
+					  &drm_bridge_connector_funcs,
+					  connector_type, ddc);
 	if (ret) {
 		kfree(bridge_connector);
 		return ERR_PTR(ret);

drivers/gpu/drm/drm_debugfs.c

@@ -762,6 +762,8 @@ static int bridges_show(struct seq_file *m, void *data)
 			drm_puts(&p, " hpd");
 		if (bridge->ops & DRM_BRIDGE_OP_MODES)
 			drm_puts(&p, " modes");
+		if (bridge->ops & DRM_BRIDGE_OP_HDMI)
+			drm_puts(&p, " hdmi");
 		drm_puts(&p, "\n");
 	}
 

include/drm/drm_bridge.h

@@ -630,6 +630,52 @@ struct drm_bridge_funcs {
 	 */
 	void (*hpd_disable)(struct drm_bridge *bridge);
 
+	/**
+	 * @hdmi_tmds_char_rate_valid:
+	 *
+	 * Check whether a particular TMDS character rate is supported by the
+	 * driver.
+	 *
+	 * This callback is optional and should only be implemented by the
+	 * bridges that take part in the HDMI connector implementation. Bridges
+	 * that implement it shall set the DRM_BRIDGE_OP_HDMI flag in their
+	 * &drm_bridge->ops.
+	 *
+	 * Returns:
+	 *
+	 * Either &drm_mode_status.MODE_OK or one of the failure reasons
+	 * in &enum drm_mode_status.
+	 */
+	enum drm_mode_status
+	(*hdmi_tmds_char_rate_valid)(const struct drm_bridge *bridge,
+				     const struct drm_display_mode *mode,
+				     unsigned long long tmds_rate);
+
+	/**
+	 * @hdmi_clear_infoframe:
+	 *
+	 * This callback clears the infoframes in the hardware during commit.
+	 * It will be called multiple times, once for every disabled infoframe
+	 * type.
+	 *
+	 * This callback is optional but it must be implemented by bridges that
+	 * set the DRM_BRIDGE_OP_HDMI flag in their &drm_bridge->ops.
+	 */
+	int (*hdmi_clear_infoframe)(struct drm_bridge *bridge,
+				    enum hdmi_infoframe_type type);
+	/**
+	 * @hdmi_write_infoframe:
+	 *
+	 * Program the infoframe into the hardware. It will be called multiple
+	 * times, once for every updated infoframe type.
+	 *
+	 * This callback is optional but it must be implemented by bridges that
+	 * set the DRM_BRIDGE_OP_HDMI flag in their &drm_bridge->ops.
+	 */
+	int (*hdmi_write_infoframe)(struct drm_bridge *bridge,
+				    enum hdmi_infoframe_type type,
+				    const u8 *buffer, size_t len);
+
 	/**
 	 * @debugfs_init:
 	 *
@@ -705,6 +751,16 @@ enum drm_bridge_ops {
 	 * this flag shall implement the &drm_bridge_funcs->get_modes callback.
 	 */
 	DRM_BRIDGE_OP_MODES = BIT(3),
+	/**
+	 * @DRM_BRIDGE_OP_HDMI: The bridge provides HDMI connector operations,
+	 * including infoframes support. Bridges that set this flag must
+	 * implement the &drm_bridge_funcs->write_infoframe callback.
+	 *
+	 * Note: currently there can be at most one bridge in a chain that sets
+	 * this bit. This is to simplify corresponding glue code in connector
+	 * drivers.
+	 */
+	DRM_BRIDGE_OP_HDMI = BIT(4),
 };
 
 /**
@@ -773,6 +829,31 @@ struct drm_bridge {
 	 * @hpd_cb.
 	 */
 	void *hpd_data;
+
+	/**
+	 * @vendor: Vendor of the product to be used for the SPD InfoFrame
+	 * generation. This is required if @DRM_BRIDGE_OP_HDMI is set.
+	 */
+	const char *vendor;
+
+	/**
+	 * @product: Name of the product to be used for the SPD InfoFrame
+	 * generation. This is required if @DRM_BRIDGE_OP_HDMI is set.
+	 */
+	const char *product;
+
+	/**
+	 * @supported_formats: Bitmask of @hdmi_colorspace listing supported
+	 * output formats. This is only relevant if @DRM_BRIDGE_OP_HDMI is set.
+	 */
+	unsigned int supported_formats;
+
+	/**
+	 * @max_bpc: Maximum bits per char the HDMI bridge supports. Allowed
+	 * values are 8, 10 and 12. This is only relevant if
+	 * @DRM_BRIDGE_OP_HDMI is set.
+	 */
+	unsigned int max_bpc;
 };
 
 static inline struct drm_bridge *