memstick: rtsx_usb_ms: Support runtime power management

In order to let host's parent device, rtsx_usb, to use USB remote wake
up signaling to do card detection, it needs to be suspended. Hence it's
necessary to add runtime PM support for the memstick host.

To keep memstick host stays suspended when it's not in use, convert the
card detection function from kthread to delayed_work, which can be
scheduled when the host is resumed and can be canceled when the host is
suspended.

Put the device to suspend when there's no card and the power mode is
MEMSTICK_POWER_OFF.
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/memstick/host/rtsx_usb_ms.c

@@ -40,15 +40,14 @@ struct rtsx_usb_ms {
 
 	struct mutex		host_mutex;
 	struct work_struct	handle_req;
-
-	struct task_struct	*detect_ms;
-	struct completion	detect_ms_exit;
+	struct delayed_work	poll_card;
 
 	u8			ssc_depth;
 	unsigned int		clock;
 	int			power_mode;
 	unsigned char           ifmode;
 	bool			eject;
+	bool			system_suspending;
 };
 
 static inline struct device *ms_dev(struct rtsx_usb_ms *host)
@@ -545,7 +544,7 @@ static void rtsx_usb_ms_handle_req(struct work_struct *work)
 						host->req->error);
 			}
 		} while (!rc);
-		pm_runtime_put(ms_dev(host));
+		pm_runtime_put_sync(ms_dev(host));
 	}
 
 }
@@ -585,14 +584,14 @@ static int rtsx_usb_ms_set_param(struct memstick_host *msh,
 			break;
 
 		if (value == MEMSTICK_POWER_ON) {
-			pm_runtime_get_sync(ms_dev(host));
+			pm_runtime_get_noresume(ms_dev(host));
 			err = ms_power_on(host);
+			if (err)
+				pm_runtime_put_noidle(ms_dev(host));
 		} else if (value == MEMSTICK_POWER_OFF) {
 			err = ms_power_off(host);
-			if (host->msh->card)
+			if (!err)
 				pm_runtime_put_noidle(ms_dev(host));
-			else
-				pm_runtime_put(ms_dev(host));
 		} else
 			err = -EINVAL;
 		if (!err)
@@ -638,12 +637,16 @@ static int rtsx_usb_ms_set_param(struct memstick_host *msh,
 	}
 out:
 	mutex_unlock(&ucr->dev_mutex);
-	pm_runtime_put(ms_dev(host));
+	pm_runtime_put_sync(ms_dev(host));
 
 	/* power-on delay */
-	if (param == MEMSTICK_POWER && value == MEMSTICK_POWER_ON)
+	if (param == MEMSTICK_POWER && value == MEMSTICK_POWER_ON) {
 		usleep_range(10000, 12000);
 
+		if (!host->eject)
+			schedule_delayed_work(&host->poll_card, 100);
+	}
+
 	dev_dbg(ms_dev(host), "%s: return = %d\n", __func__, err);
 	return err;
 }
@@ -654,9 +657,24 @@ static int rtsx_usb_ms_suspend(struct device *dev)
 	struct rtsx_usb_ms *host = dev_get_drvdata(dev);
 	struct memstick_host *msh = host->msh;
 
-	dev_dbg(ms_dev(host), "--> %s\n", __func__);
+	/* Since we use rtsx_usb's resume callback to runtime resume its
+	 * children to implement remote wakeup signaling, this causes
+	 * rtsx_usb_ms' runtime resume callback runs after its suspend
+	 * callback:
+	 * rtsx_usb_ms_suspend()
+	 * rtsx_usb_resume()
+	 *   -> rtsx_usb_ms_runtime_resume()
+	 *     -> memstick_detect_change()
+	 *
+	 * rtsx_usb_suspend()
+	 *
+	 * To avoid this, skip runtime resume/suspend if system suspend is
+	 * underway.
+	 */
 
+	host->system_suspending = true;
 	memstick_suspend_host(msh);
+
 	return 0;
 }
 
@@ -665,26 +683,58 @@ static int rtsx_usb_ms_resume(struct device *dev)
 	struct rtsx_usb_ms *host = dev_get_drvdata(dev);
 	struct memstick_host *msh = host->msh;
 
-	dev_dbg(ms_dev(host), "--> %s\n", __func__);
-
 	memstick_resume_host(msh);
+	host->system_suspending = false;
+
 	return 0;
 }
 #endif /* CONFIG_PM_SLEEP */
 
-/*
- * Thread function of ms card slot detection. The thread starts right after
- * successful host addition. It stops while the driver removal function sets
- * host->eject true.
- */
-static int rtsx_usb_detect_ms_card(void *__host)
+#ifdef CONFIG_PM
+static int rtsx_usb_ms_runtime_suspend(struct device *dev)
 {
-	struct rtsx_usb_ms *host = (struct rtsx_usb_ms *)__host;
+	struct rtsx_usb_ms *host = dev_get_drvdata(dev);
+
+	if (host->system_suspending)
+		return 0;
+
+	if (host->msh->card || host->power_mode != MEMSTICK_POWER_OFF)
+		return -EAGAIN;
+
+	return 0;
+}
+
+static int rtsx_usb_ms_runtime_resume(struct device *dev)
+{
+	struct rtsx_usb_ms *host = dev_get_drvdata(dev);
+
+
+	if (host->system_suspending)
+		return 0;
+
+	memstick_detect_change(host->msh);
+
+	return 0;
+}
+#endif /* CONFIG_PM */
+
+static const struct dev_pm_ops rtsx_usb_ms_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(rtsx_usb_ms_suspend, rtsx_usb_ms_resume)
+	SET_RUNTIME_PM_OPS(rtsx_usb_ms_runtime_suspend, rtsx_usb_ms_runtime_resume, NULL)
+};
+
+
+static void rtsx_usb_ms_poll_card(struct work_struct *work)
+{
+	struct rtsx_usb_ms *host = container_of(work, struct rtsx_usb_ms,
+			poll_card.work);
 	struct rtsx_ucr *ucr = host->ucr;
-	u8 val = 0;
 	int err;
+	u8 val;
+
+	if (host->eject || host->power_mode != MEMSTICK_POWER_ON)
+		return;
 
-	for (;;) {
 	pm_runtime_get_sync(ms_dev(host));
 	mutex_lock(&ucr->dev_mutex);
 
@@ -708,15 +758,10 @@ static int rtsx_usb_detect_ms_card(void *__host)
 	}
 
 poll_again:
-		pm_runtime_put(ms_dev(host));
-		if (host->eject)
-			break;
-
-		schedule_timeout_idle(HZ);
-	}
+	pm_runtime_put_sync(ms_dev(host));
 
-	complete(&host->detect_ms_exit);
-	return 0;
+	if (!host->eject && host->power_mode == MEMSTICK_POWER_ON)
+		schedule_delayed_work(&host->poll_card, 100);
 }
 
 static int rtsx_usb_ms_drv_probe(struct platform_device *pdev)
@@ -747,40 +792,36 @@ static int rtsx_usb_ms_drv_probe(struct platform_device *pdev)
 	mutex_init(&host->host_mutex);
 	INIT_WORK(&host->handle_req, rtsx_usb_ms_handle_req);
 
-	init_completion(&host->detect_ms_exit);
-	host->detect_ms = kthread_create(rtsx_usb_detect_ms_card, host,
-			"rtsx_usb_ms_%d", pdev->id);
-	if (IS_ERR(host->detect_ms)) {
-		dev_dbg(&(pdev->dev),
-				"Unable to create polling thread.\n");
-		err = PTR_ERR(host->detect_ms);
-		goto err_out;
-	}
+	INIT_DELAYED_WORK(&host->poll_card, rtsx_usb_ms_poll_card);
 
 	msh->request = rtsx_usb_ms_request;
 	msh->set_param = rtsx_usb_ms_set_param;
 	msh->caps = MEMSTICK_CAP_PAR4;
 
-	pm_runtime_enable(&pdev->dev);
+	pm_runtime_get_noresume(ms_dev(host));
+	pm_runtime_set_active(ms_dev(host));
+	pm_runtime_enable(ms_dev(host));
+
 	err = memstick_add_host(msh);
 	if (err)
 		goto err_out;
 
-	wake_up_process(host->detect_ms);
+	pm_runtime_put(ms_dev(host));
+
 	return 0;
 err_out:
 	memstick_free_host(msh);
 	pm_runtime_disable(ms_dev(host));
+	pm_runtime_put_noidle(ms_dev(host));
 	return err;
 }
 
 static int rtsx_usb_ms_drv_remove(struct platform_device *pdev)
 {
 	struct rtsx_usb_ms *host = platform_get_drvdata(pdev);
-	struct memstick_host *msh;
+	struct memstick_host *msh = host->msh;
 	int err;
 
-	msh = host->msh;
 	host->eject = true;
 	cancel_work_sync(&host->handle_req);
 
@@ -798,7 +839,6 @@ static int rtsx_usb_ms_drv_remove(struct platform_device *pdev)
 	}
 	mutex_unlock(&host->host_mutex);
 
-	wait_for_completion(&host->detect_ms_exit);
 	memstick_remove_host(msh);
 	memstick_free_host(msh);
 
@@ -817,9 +857,6 @@ static int rtsx_usb_ms_drv_remove(struct platform_device *pdev)
 	return 0;
 }
 
-static SIMPLE_DEV_PM_OPS(rtsx_usb_ms_pm_ops,
-		rtsx_usb_ms_suspend, rtsx_usb_ms_resume);
-
 static struct platform_device_id rtsx_usb_ms_ids[] = {
 	{
 		.name = "rtsx_usb_ms",