media: i2c: imx290: Use runtime PM autosuspend

Use runtime PM autosuspend to avoid powering off the sensor during fast
stop-reconfigure-restart cycles. This also fixes runtime PM handling in
the probe function that didn't suspend the device, effectively leaving
it resumed forever.

While at it, improve documentation of power management in probe() and
remove().
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/i2c/imx290.c

@@ -626,7 +626,8 @@ static int imx290_set_ctrl(struct v4l2_ctrl *ctrl)
 		break;
 	}
 
-	pm_runtime_put(imx290->dev);
+	pm_runtime_mark_last_busy(imx290->dev);
+	pm_runtime_put_autosuspend(imx290->dev);
 
 	return ret;
 }
@@ -827,12 +828,13 @@ static int imx290_set_stream(struct v4l2_subdev *sd, int enable)
 		ret = imx290_start_streaming(imx290, state);
 		if (ret) {
 			dev_err(imx290->dev, "Start stream failed\n");
-			pm_runtime_put(imx290->dev);
+			pm_runtime_put_sync(imx290->dev);
 			goto unlock;
 		}
 	} else {
 		imx290_stop_streaming(imx290);
-		pm_runtime_put(imx290->dev);
+		pm_runtime_mark_last_busy(imx290->dev);
+		pm_runtime_put_autosuspend(imx290->dev);
 	}
 
 unlock:
@@ -1269,33 +1271,59 @@ static int imx290_probe(struct i2c_client *client)
 	if (ret)
 		return ret;
 
-	/* Initialize and register subdev. */
+	/* Initialize the V4L2 subdev. */
 	ret = imx290_subdev_init(imx290);
 	if (ret)
 		return ret;
 
-	ret = v4l2_async_register_subdev(&imx290->sd);
-	if (ret < 0) {
-		dev_err(dev, "Could not register v4l2 device\n");
-		goto err_subdev;
-	}
-
-	/* Power on the device to match runtime PM state below */
+	/*
+	 * Enable power management. The driver supports runtime PM, but needs to
+	 * work when runtime PM is disabled in the kernel. To that end, power
+	 * the sensor on manually here.
+	 */
 	ret = imx290_power_on(dev);
 	if (ret < 0) {
 		dev_err(dev, "Could not power on the device\n");
 		goto err_subdev;
 	}
 
+	/*
+	 * Enable runtime PM with autosuspend. As the device has been powered
+	 * manually, mark it as active, and increase the usage count without
+	 * resuming the device.
+	 */
 	pm_runtime_set_active(dev);
+	pm_runtime_get_noresume(dev);
 	pm_runtime_enable(dev);
-	pm_runtime_idle(dev);
+	pm_runtime_set_autosuspend_delay(dev, 1000);
+	pm_runtime_use_autosuspend(dev);
+
+	/*
+	 * Finally, register the V4L2 subdev. This must be done after
+	 * initializing everything as the subdev can be used immediately after
+	 * being registered.
+	 */
+	ret = v4l2_async_register_subdev(&imx290->sd);
+	if (ret < 0) {
+		dev_err(dev, "Could not register v4l2 device\n");
+		goto err_pm;
+	}
+
+	/*
+	 * Decrease the PM usage count. The device will get suspended after the
+	 * autosuspend delay, turning the power off.
+	 */
+	pm_runtime_mark_last_busy(dev);
+	pm_runtime_put_autosuspend(dev);
 
 	return 0;
 
+err_pm:
+	pm_runtime_disable(dev);
+	pm_runtime_put_noidle(dev);
+	imx290_power_off(dev);
 err_subdev:
 	imx290_subdev_cleanup(imx290);
-
 	return ret;
 }
 
@@ -1307,6 +1335,10 @@ static void imx290_remove(struct i2c_client *client)
 	v4l2_async_unregister_subdev(sd);
 	imx290_subdev_cleanup(imx290);
 
+	/*
+	 * Disable runtime PM. In case runtime PM is disabled in the kernel,
+	 * make sure to turn power off manually.
+	 */
 	pm_runtime_disable(imx290->dev);
 	if (!pm_runtime_status_suspended(imx290->dev))
 		imx290_power_off(imx290->dev);