drm/bridge: imx8mp-hdmi-pai: enable PM runtime

There is an audio channel shift issue with multi channel case - the
channel order is correct for the first run, but the channel order is
shifted for the second run. The fix method is to reset the PAI interface
at the end of playback.

The reset can be handled by PM runtime, so enable PM runtime.

Fixes: 0205fae6327a ("drm/bridge: imx: add driver for HDMI TX Parallel Audio Interface")
Signed-off-by: Shengjiu Wang <[e-mail]>
Reviewed-by: Liu Ying <[e-mail]>
Signed-off-by: Liu Ying <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/gpu/drm/bridge/imx/imx8mp-hdmi-pai.c

···
 #include <linux/module.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
 #include <linux/regmap.h>
 #include <drm/bridge/dw_hdmi.h>
 #include <sound/asoundef.h>
···
 
 struct imx8mp_hdmi_pai {
 	struct regmap	*regmap;
+	struct device	*dev;
 };
 
 static void imx8mp_hdmi_pai_enable(struct dw_hdmi *dw_hdmi, int channel,
···
 	const struct dw_hdmi_plat_data *pdata = dw_hdmi_to_plat_data(dw_hdmi);
 	struct imx8mp_hdmi_pai *hdmi_pai = pdata->priv_audio;
 	int val;
+
+	if (pm_runtime_resume_and_get(hdmi_pai->dev) < 0)
+		return;
 
 	/* PAI set control extended */
 	val =  WTMK_HIGH(3) | WTMK_LOW(3);
···
 
 	/* Stop PAI */
 	regmap_write(hdmi_pai->regmap, HTX_PAI_CTRL, 0);
+
+	pm_runtime_put_sync(hdmi_pai->dev);
 }
 
 static const struct regmap_config imx8mp_hdmi_pai_regmap_config = {
···
 	struct imx8mp_hdmi_pai *hdmi_pai;
 	struct resource *res;
 	void __iomem *base;
+	int ret;
 
 	hdmi_pai = devm_kzalloc(dev, sizeof(*hdmi_pai), GFP_KERNEL);
 	if (!hdmi_pai)
···
 	plat_data->enable_audio = imx8mp_hdmi_pai_enable;
 	plat_data->disable_audio = imx8mp_hdmi_pai_disable;
 	plat_data->priv_audio = hdmi_pai;
+
+	hdmi_pai->dev = dev;
+	ret = devm_pm_runtime_enable(dev);
+	if (ret < 0) {
+		dev_err(dev, "failed to enable PM runtime: %d\n", ret);
+		return ret;
+	}
 
 	return 0;
 }