drm/i2c: tda998x: only enable audio if supported by sink

Check for audio support by the attached sink by consulting the EDID
prior to enabling audio over the TMDS link.  We must consult the EDID
after calling drm_helper_probe_single_connector_modes(), as this can
use an override EDID, or load a replacement EDID.
Tested-by: Jon Medhurst <tixy@linaro.org>
Acked-by: Jon Medhurst <tixy@linaro.org>
Tested-by: Jyri Sarha <jsarha@ti.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

drivers/gpu/drm/i2c/tda998x_drv.c

@@ -44,6 +44,7 @@ struct tda998x_priv {
 	u8 current_page;
 	int dpms;
 	bool supports_infoframes;
+	bool sink_has_audio;
 	u8 vip_cntrl_0;
 	u8 vip_cntrl_1;
 	u8 vip_cntrl_2;
@@ -1090,13 +1091,33 @@ tda998x_encoder_mode_set(struct drm_encoder *encoder,
 
 		tda998x_write_avi(priv, adjusted_mode);
 
-		if (priv->audio_params.format != AFMT_UNUSED)
+		if (priv->audio_params.format != AFMT_UNUSED &&
+		    priv->sink_has_audio)
 			tda998x_configure_audio(priv, &priv->audio_params);
 	}
 
 	mutex_unlock(&priv->audio_mutex);
 }
 
+static int tda998x_connector_fill_modes(struct drm_connector *connector,
+					uint32_t maxX, uint32_t maxY)
+{
+	struct tda998x_priv *priv = conn_to_tda998x_priv(connector);
+	int ret;
+
+	ret = drm_helper_probe_single_connector_modes(connector, maxX, maxY);
+
+	if (connector->edid_blob_ptr) {
+		struct edid *edid = (void *)connector->edid_blob_ptr->data;
+
+		priv->sink_has_audio = drm_detect_monitor_audio(edid);
+	} else {
+		priv->sink_has_audio = false;
+	}
+
+	return ret;
+}
+
 static enum drm_connector_status
 tda998x_connector_detect(struct drm_connector *connector, bool force)
 {
@@ -1274,7 +1295,7 @@ static int tda998x_audio_hw_params(struct device *dev, void *data,
 	}
 
 	mutex_lock(&priv->audio_mutex);
-	if (priv->supports_infoframes)
+	if (priv->supports_infoframes && priv->sink_has_audio)
 		ret = tda998x_configure_audio(priv, &audio);
 	else
 		ret = 0;
@@ -1608,7 +1629,7 @@ static int tda998x_connector_dpms(struct drm_connector *connector, int mode)
 static const struct drm_connector_funcs tda998x_connector_funcs = {
 	.dpms = tda998x_connector_dpms,
 	.reset = drm_atomic_helper_connector_reset,
-	.fill_modes = drm_helper_probe_single_connector_modes,
+	.fill_modes = tda998x_connector_fill_modes,
 	.detect = tda998x_connector_detect,
 	.destroy = tda998x_connector_destroy,
 	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,