drm/connector: implement generic HDMI audio helpers

Several DRM drivers implement HDMI codec support (despite its name it
applies to both HDMI and DisplayPort drivers). Implement generic
framework to be used by these drivers. This removes a requirement to
implement get_eld() callback and provides default implementation for
codec's plug handling.

Acked-by: Maxime Ripard <mripard@kernel.org>
Tested-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241224-drm-bridge-hdmi-connector-v10-3-dc89577cd438@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

drivers/gpu/drm/display/Kconfig

@@ -75,6 +75,12 @@ config DRM_DISPLAY_HDCP_HELPER
 	help
 	  DRM display helpers for HDCP.
 
+config DRM_DISPLAY_HDMI_AUDIO_HELPER
+	bool
+	help
+	  DRM display helpers for HDMI Audio functionality (generic HDMI Codec
+	  implementation).
+
 config DRM_DISPLAY_HDMI_HELPER
 	bool
 	help

drivers/gpu/drm/display/Makefile

@@ -14,6 +14,8 @@ drm_display_helper-$(CONFIG_DRM_DISPLAY_DP_TUNNEL) += \
 drm_display_helper-$(CONFIG_DRM_DISPLAY_DSC_HELPER) += \
 	drm_dsc_helper.o
 drm_display_helper-$(CONFIG_DRM_DISPLAY_HDCP_HELPER) += drm_hdcp_helper.o
+drm_display_helper-$(CONFIG_DRM_DISPLAY_HDMI_AUDIO_HELPER) += \
+	drm_hdmi_audio_helper.o
 drm_display_helper-$(CONFIG_DRM_DISPLAY_HDMI_HELPER) += \
 	drm_hdmi_helper.o \
 	drm_scdc_helper.o

drivers/gpu/drm/display/drm_hdmi_audio_helper.c

@@ -0,0 +1,190 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright (c) 2024 Linaro Ltd
+ */
+
+#include <linux/mutex.h>
+#include <linux/of_graph.h>
+#include <linux/platform_device.h>
+
+#include <drm/drm_connector.h>
+#include <drm/drm_device.h>
+#include <drm/display/drm_hdmi_audio_helper.h>
+
+#include <sound/hdmi-codec.h>
+
+static int drm_connector_hdmi_audio_startup(struct device *dev, void *data)
+{
+	struct drm_connector *connector = data;
+	const struct drm_connector_hdmi_audio_funcs *funcs =
+		connector->hdmi_audio.funcs;
+
+	if (funcs->startup)
+		return funcs->startup(connector);
+
+	return 0;
+}
+
+static int drm_connector_hdmi_audio_prepare(struct device *dev, void *data,
+					    struct hdmi_codec_daifmt *fmt,
+					    struct hdmi_codec_params *hparms)
+{
+	struct drm_connector *connector = data;
+	const struct drm_connector_hdmi_audio_funcs *funcs =
+		connector->hdmi_audio.funcs;
+
+	return funcs->prepare(connector, fmt, hparms);
+}
+
+static void drm_connector_hdmi_audio_shutdown(struct device *dev, void *data)
+{
+	struct drm_connector *connector = data;
+	const struct drm_connector_hdmi_audio_funcs *funcs =
+		connector->hdmi_audio.funcs;
+
+	return funcs->shutdown(connector);
+}
+
+static int drm_connector_hdmi_audio_mute_stream(struct device *dev, void *data,
+						bool enable, int direction)
+{
+	struct drm_connector *connector = data;
+	const struct drm_connector_hdmi_audio_funcs *funcs =
+		connector->hdmi_audio.funcs;
+
+	if (funcs->mute_stream)
+		return funcs->mute_stream(connector, enable, direction);
+
+	return -ENOTSUPP;
+}
+
+static int drm_connector_hdmi_audio_get_dai_id(struct snd_soc_component *comment,
+					       struct device_node *endpoint,
+					       void *data)
+{
+	struct drm_connector *connector = data;
+	struct of_endpoint of_ep;
+	int ret;
+
+	if (connector->hdmi_audio.dai_port < 0)
+		return -ENOTSUPP;
+
+	ret = of_graph_parse_endpoint(endpoint, &of_ep);
+	if (ret < 0)
+		return ret;
+
+	if (of_ep.port == connector->hdmi_audio.dai_port)
+		return 0;
+
+	return -EINVAL;
+}
+
+static int drm_connector_hdmi_audio_get_eld(struct device *dev, void *data,
+					    uint8_t *buf, size_t len)
+{
+	struct drm_connector *connector = data;
+
+	mutex_lock(&connector->eld_mutex);
+	memcpy(buf, connector->eld, min(sizeof(connector->eld), len));
+	mutex_unlock(&connector->eld_mutex);
+
+	return 0;
+}
+
+static int drm_connector_hdmi_audio_hook_plugged_cb(struct device *dev,
+						    void *data,
+						    hdmi_codec_plugged_cb fn,
+						    struct device *codec_dev)
+{
+	struct drm_connector *connector = data;
+
+	mutex_lock(&connector->hdmi_audio.lock);
+
+	connector->hdmi_audio.plugged_cb = fn;
+	connector->hdmi_audio.plugged_cb_dev = codec_dev;
+
+	fn(codec_dev, connector->hdmi_audio.last_state);
+
+	mutex_unlock(&connector->hdmi_audio.lock);
+
+	return 0;
+}
+
+void drm_connector_hdmi_audio_plugged_notify(struct drm_connector *connector,
+					     bool plugged)
+{
+	mutex_lock(&connector->hdmi_audio.lock);
+
+	connector->hdmi_audio.last_state = plugged;
+
+	if (connector->hdmi_audio.plugged_cb &&
+	    connector->hdmi_audio.plugged_cb_dev)
+		connector->hdmi_audio.plugged_cb(connector->hdmi_audio.plugged_cb_dev,
+						 connector->hdmi_audio.last_state);
+
+	mutex_unlock(&connector->hdmi_audio.lock);
+}
+EXPORT_SYMBOL(drm_connector_hdmi_audio_plugged_notify);
+
+static const struct hdmi_codec_ops drm_connector_hdmi_audio_ops = {
+	.audio_startup = drm_connector_hdmi_audio_startup,
+	.prepare = drm_connector_hdmi_audio_prepare,
+	.audio_shutdown = drm_connector_hdmi_audio_shutdown,
+	.mute_stream = drm_connector_hdmi_audio_mute_stream,
+	.get_eld = drm_connector_hdmi_audio_get_eld,
+	.get_dai_id = drm_connector_hdmi_audio_get_dai_id,
+	.hook_plugged_cb = drm_connector_hdmi_audio_hook_plugged_cb,
+};
+
+/**
+ * drm_connector_hdmi_audio_init - Initialize HDMI Codec device for the DRM connector
+ * @connector: A pointer to the connector to allocate codec for
+ * @hdmi_codec_dev: device to be used as a parent for the HDMI Codec
+ * @funcs: callbacks for this HDMI Codec
+ * @max_i2s_playback_channels: maximum number of playback I2S channels
+ * @spdif_playback: set if HDMI codec has S/PDIF playback port
+ * @dai_port: sound DAI port, -1 if it is not enabled
+ *
+ * Create a HDMI codec device to be used with the specified connector.
+ *
+ * Returns:
+ * Zero on success, error code on failure.
+ */
+int drm_connector_hdmi_audio_init(struct drm_connector *connector,
+				  struct device *hdmi_codec_dev,
+				  const struct drm_connector_hdmi_audio_funcs *funcs,
+				  unsigned int max_i2s_playback_channels,
+				  bool spdif_playback,
+				  int dai_port)
+{
+	struct hdmi_codec_pdata codec_pdata = {
+		.ops = &drm_connector_hdmi_audio_ops,
+		.max_i2s_channels = max_i2s_playback_channels,
+		.i2s = !!max_i2s_playback_channels,
+		.spdif = spdif_playback,
+		.no_i2s_capture = true,
+		.no_spdif_capture = true,
+		.data = connector,
+	};
+	struct platform_device *pdev;
+
+	if (!funcs ||
+	    !funcs->prepare ||
+	    !funcs->shutdown)
+		return -EINVAL;
+
+	connector->hdmi_audio.funcs = funcs;
+	connector->hdmi_audio.dai_port = dai_port;
+
+	pdev = platform_device_register_data(hdmi_codec_dev,
+					     HDMI_CODEC_DRV_NAME,
+					     PLATFORM_DEVID_AUTO,
+					     &codec_pdata, sizeof(codec_pdata));
+	if (IS_ERR(pdev))
+		return PTR_ERR(pdev);
+
+	connector->hdmi_audio.codec_pdev = pdev;
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_connector_hdmi_audio_init);

drivers/gpu/drm/drm_connector.c

@@ -33,6 +33,7 @@
 #include <drm/drm_sysfs.h>
 #include <drm/drm_utils.h>
 
+#include <linux/platform_device.h>
 #include <linux/property.h>
 #include <linux/uaccess.h>
 
@@ -281,6 +282,7 @@ static int drm_connector_init_only(struct drm_device *dev,
 	mutex_init(&connector->eld_mutex);
 	mutex_init(&connector->edid_override_mutex);
 	mutex_init(&connector->hdmi.infoframes.lock);
+	mutex_init(&connector->hdmi_audio.lock);
 	connector->edid_blob_ptr = NULL;
 	connector->epoch_counter = 0;
 	connector->tile_blob_ptr = NULL;
@@ -714,6 +716,8 @@ void drm_connector_cleanup(struct drm_connector *connector)
 		    DRM_CONNECTOR_REGISTERED))
 		drm_connector_unregister(connector);
 
+	platform_device_unregister(connector->hdmi_audio.codec_pdev);
+
 	if (connector->privacy_screen) {
 		drm_privacy_screen_put(connector->privacy_screen);
 		connector->privacy_screen = NULL;
@@ -750,6 +754,7 @@ void drm_connector_cleanup(struct drm_connector *connector)
 		connector->funcs->atomic_destroy_state(connector,
 						       connector->state);
 
+	mutex_destroy(&connector->hdmi_audio.lock);
 	mutex_destroy(&connector->hdmi.infoframes.lock);
 	mutex_destroy(&connector->mutex);
 

include/drm/display/drm_hdmi_audio_helper.h

@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: MIT */
+
+#ifndef DRM_DISPLAY_HDMI_AUDIO_HELPER_H_
+#define DRM_DISPLAY_HDMI_AUDIO_HELPER_H_
+
+#include <linux/types.h>
+
+struct drm_connector;
+struct drm_connector_hdmi_audio_funcs;
+
+struct device;
+
+int drm_connector_hdmi_audio_init(struct drm_connector *connector,
+				  struct device *hdmi_codec_dev,
+				  const struct drm_connector_hdmi_audio_funcs *funcs,
+				  unsigned int max_i2s_playback_channels,
+				  bool spdif_playback,
+				  int sound_dai_port);
+void drm_connector_hdmi_audio_plugged_notify(struct drm_connector *connector,
+					     bool plugged);
+
+#endif