drm/bridge: it6505: Adapt runtime power management framework

Use pm_runtime_(get|put)_sync to control the bridge power, and add
SET_SYSTEM_SLEEP_PM_OPS with pm_runtime_force_(suspend|resume) to it6505
driver. Without SET_SYSTEM_SLEEP_PM_OPS, the bridge will be powered on
unnecessarily when no external display is connected.

Fixes: b5c84a9e ("drm/bridge: add it6505 driver")
Signed-off-by: Pin-yen Lin <treapking@chromium.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221004044943.2407781-2-treapking@chromium.org

drivers/gpu/drm/bridge/ite-it6505.c

@@ -421,6 +421,7 @@ struct it6505 {
 	struct notifier_block event_nb;
 	struct extcon_dev *extcon;
 	struct work_struct extcon_wq;
+	int extcon_state;
 	enum drm_connector_status connector_status;
 	enum link_train_status link_state;
 	struct work_struct link_works;
@@ -2685,31 +2686,41 @@ static void it6505_extcon_work(struct work_struct *work)
 {
 	struct it6505 *it6505 = container_of(work, struct it6505, extcon_wq);
 	struct device *dev = &it6505->client->dev;
-	int state = extcon_get_state(it6505->extcon, EXTCON_DISP_DP);
-	unsigned int pwroffretry = 0;
+	int state, ret;
 
 	if (it6505->enable_drv_hold)
 		return;
 
 	mutex_lock(&it6505->extcon_lock);
 
+	state = extcon_get_state(it6505->extcon, EXTCON_DISP_DP);
 	DRM_DEV_DEBUG_DRIVER(dev, "EXTCON_DISP_DP = 0x%02x", state);
-	if (state > 0) {
+
+	if (state == it6505->extcon_state || unlikely(state < 0))
+		goto unlock;
+	it6505->extcon_state = state;
+	if (state) {
 		DRM_DEV_DEBUG_DRIVER(dev, "start to power on");
 		msleep(100);
-		it6505_poweron(it6505);
+		ret = pm_runtime_get_sync(dev);
+
+		/*
+		 * On system resume, extcon_work can be triggered before
+		 * pm_runtime_force_resume re-enables runtime power management.
+		 * Handling the error here to make sure the bridge is powered on.
+		 */
+		if (ret)
+			it6505_poweron(it6505);
 	} else {
 		DRM_DEV_DEBUG_DRIVER(dev, "start to power off");
-		while (it6505_poweroff(it6505) && pwroffretry++ < 5) {
-			DRM_DEV_DEBUG_DRIVER(dev, "power off fail %d times",
-					     pwroffretry);
-		}
+		pm_runtime_put_sync(dev);
 
 		drm_helper_hpd_irq_event(it6505->bridge.dev);
 		memset(it6505->dpcd, 0, sizeof(it6505->dpcd));
 		DRM_DEV_DEBUG_DRIVER(dev, "power off it6505 success!");
 	}
 
+unlock:
 	mutex_unlock(&it6505->extcon_lock);
 }
 
@@ -3032,8 +3043,10 @@ static __maybe_unused int it6505_bridge_suspend(struct device *dev)
 	return it6505_poweroff(it6505);
 }
 
-static SIMPLE_DEV_PM_OPS(it6505_bridge_pm_ops, it6505_bridge_suspend,
-			 it6505_bridge_resume);
+static const struct dev_pm_ops it6505_bridge_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)
+	SET_RUNTIME_PM_OPS(it6505_bridge_suspend, it6505_bridge_resume, NULL)
+};
 
 static int it6505_init_pdata(struct it6505 *it6505)
 {
@@ -3315,6 +3328,7 @@ static int it6505_i2c_probe(struct i2c_client *client,
 
 	DRM_DEV_DEBUG_DRIVER(dev, "it6505 device name: %s", dev_name(dev));
 	debugfs_init(it6505);
+	pm_runtime_enable(dev);
 
 	it6505->bridge.funcs = &it6505_bridge_funcs;
 	it6505->bridge.type = DRM_MODE_CONNECTOR_DisplayPort;