drm: bridge/dw_hdmi: introduce interface to setting sample rate

Introduce dw_hdmi_set_sample_rate(), which allows us to configure the
audio sample rate, setting the CTS/N values appropriately.
Tested-by: Yakir Yang <ykk@rock-chips.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/gpu/drm/bridge/dw_hdmi.c

@@ -365,6 +365,16 @@ static void hdmi_clk_regenerator_update_pixel_clock(struct dw_hdmi *hdmi)
 	mutex_unlock(&hdmi->audio_mutex);
 }
 
+void dw_hdmi_set_sample_rate(struct dw_hdmi *hdmi, unsigned int rate)
+{
+	mutex_lock(&hdmi->audio_mutex);
+	hdmi->sample_rate = rate;
+	hdmi_set_clk_regenerator(hdmi, hdmi->hdmi_data.video_mode.mpixelclock,
+				 hdmi->sample_rate, hdmi->ratio);
+	mutex_unlock(&hdmi->audio_mutex);
+}
+EXPORT_SYMBOL_GPL(dw_hdmi_set_sample_rate);
+
 /*
  * this submodule is responsible for the video data synchronization.
  * for example, for RGB 4:4:4 input, the data map is defined as

include/drm/bridge/dw_hdmi.h

@@ -12,6 +12,8 @@
 
 #include <drm/drmP.h>
 
+struct dw_hdmi;
+
 enum {
 	DW_HDMI_RES_8,
 	DW_HDMI_RES_10,
@@ -59,4 +61,7 @@ int dw_hdmi_bind(struct device *dev, struct device *master,
 		 void *data, struct drm_encoder *encoder,
 		 struct resource *iores, int irq,
 		 const struct dw_hdmi_plat_data *plat_data);
+
+void dw_hdmi_set_sample_rate(struct dw_hdmi *hdmi, unsigned int rate);
+
 #endif /* __IMX_HDMI_H__ */