drm: apple: disable HDMI audio by default

Can be still enabled by adding `apple_dcp.hdmi_audio` the kernel command
line.

Signed-off-by: Janne Grunau <j@jannau.net>

Author: jannau

drivers/gpu/drm/apple/audio.c

@@ -494,11 +494,16 @@ static void dcpaud_set_card_names(struct dcp_audio *dcpaud)
 	strscpy(card->shortname, "Apple DisplayPort", sizeof(card->shortname));
 }
 
+extern bool hdmi_audio;
+
 static int dcpaud_init_snd_card(struct dcp_audio *dcpaud)
 {
 	int ret;
 	struct dma_chan *chan;
 
+	if (!hdmi_audio)
+		return -ENODEV;
+
 	chan = of_dma_request_slave_channel(dcpaud->dev->of_node, "tx");
 	/* squelch dma channel request errors, the driver will try again alter */
 	if (!chan) {

drivers/gpu/drm/apple/dcp.c

@@ -46,9 +46,9 @@ static bool show_notch;
 module_param(show_notch, bool, 0644);
 MODULE_PARM_DESC(show_notch, "Use the full display height and shows the notch");
 
-static bool noaudio;
-module_param(noaudio, bool, 0644);
-MODULE_PARM_DESC(noaudio, "Skip audio support");
+bool hdmi_audio;
+module_param(hdmi_audio, bool, 0644);
+MODULE_PARM_DESC(hdmi_audio, "Enable unstable HDMI audio support");
 
 /* HACK: moved here to avoid circular dependency between apple_drv and dcp */
 void dcp_drm_crtc_vblank(struct apple_crtc *crtc)
@@ -413,7 +413,7 @@ int dcp_start(struct platform_device *pdev)
 		dev_err(dcp->dev, "Failed to start IOMFB endpoint: %d\n", ret);
 
 #if IS_ENABLED(CONFIG_DRM_APPLE_AUDIO)
-	if (!noaudio) {
+	if (hdmi_audio) {
 		ret = avep_init(dcp);
 		if (ret)
 			dev_warn(dcp->dev, "Failed to start AV endpoint: %d", ret);