netdev - [PATCH] can: flexcan: fix deadlock when using self wakeup

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Date:   Fri, 17 May 2019 02:39:10 +0000
From:   Joakim Zhang <qiangqing.zhang@....com>
To:     "mkl@...gutronix.de" <mkl@...gutronix.de>,
        "linux-can@...r.kernel.org" <linux-can@...r.kernel.org>
CC:     dl-linux-imx <linux-imx@....com>,
        "wg@...ndegger.com" <wg@...ndegger.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Joakim Zhang <qiangqing.zhang@....com>
Subject: [PATCH] can: flexcan: fix deadlock when using self wakeup

As reproted by Sean Nyekjaer bellow:
When suspending, when there is still can traffic on the
interfaces the flexcan immediately wakes the platform again.
As it should :-)
But it throws this error msg:
[ 3169.378661] PM: noirq suspend of devices failed

On the way down to suspend the interface that throws the error
message does call flexcan_suspend but fails to call
flexcan_noirq_suspend.
That means the flexcan_enter_stop_mode is called, but on the way
out of suspend the driver only calls flexcan_resume and skips
flexcan_noirq_resume, thus it doesn't call flexcan_exit_stop_mode.
This leaves the flexcan in stop mode, and with the current driver
it can't recover from this even with a soft reboot, it requires a
hard reboot.

Fixes: de3578c198c6 ("can: flexcan: add self wakeup support")

This patch intends to fix the issue, and also add comment to explain the
wakeup flow.

Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
---
 drivers/net/can/flexcan.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
index e35083ff31ee..6fbce473a8c7 100644
--- a/drivers/net/can/flexcan.c
+++ b/drivers/net/can/flexcan.c
@@ -286,6 +286,7 @@ struct flexcan_priv {
 	const struct flexcan_devtype_data *devtype_data;
 	struct regulator *reg_xceiver;
 	struct flexcan_stop_mode stm;
+	bool in_stop_mode;
 
 	/* Read and Write APIs */
 	u32 (*read)(void __iomem *addr);
@@ -1653,6 +1654,7 @@ static int __maybe_unused flexcan_suspend(struct device *device)
 		if (device_may_wakeup(device)) {
 			enable_irq_wake(dev->irq);
 			flexcan_enter_stop_mode(priv);
+			priv->in_stop_mode = true;
 		} else {
 			err = flexcan_chip_disable(priv);
 			if (err)
@@ -1679,6 +1681,11 @@ static int __maybe_unused flexcan_resume(struct device *device)
 		netif_device_attach(dev);
 		netif_start_queue(dev);
 		if (device_may_wakeup(device)) {
+			if (priv->in_stop_mode) {
+				flexcan_enable_wakeup_irq(priv, false);
+				flexcan_exit_stop_mode(priv);
+				priv->in_stop_mode = false;
+			}
 			disable_irq_wake(dev->irq);
 		} else {
 			err = pm_runtime_force_resume(device);
@@ -1715,6 +1722,11 @@ static int __maybe_unused flexcan_noirq_suspend(struct device *device)
 	struct net_device *dev = dev_get_drvdata(device);
 	struct flexcan_priv *priv = netdev_priv(dev);
 
+	/* Need enable wakeup interrupt in noirq suspend stage. Otherwise,
+	 * it will trigger continuously wakeup interrupt if the wakeup event
+	 * comes before noirq suspend stage, and simultaneously in has enter
+	 * the stop mode.
+	 */
 	if (netif_running(dev) && device_may_wakeup(device))
 		flexcan_enable_wakeup_irq(priv, true);
 
@@ -1726,9 +1738,14 @@ static int __maybe_unused flexcan_noirq_resume(struct device *device)
 	struct net_device *dev = dev_get_drvdata(device);
 	struct flexcan_priv *priv = netdev_priv(dev);
 
+	/* Need exit stop mode in noirq resume stage. Otherwise, it will
+	 * trigger continuously wakeup interrupt if the wakeup event comes,
+	 * and simultaneously it has still in stop mode.
+	 */
 	if (netif_running(dev) && device_may_wakeup(device)) {
 		flexcan_enable_wakeup_irq(priv, false);
 		flexcan_exit_stop_mode(priv);
+		priv->in_stop_mode = false;
 	}
 
 	return 0;
-- 
2.17.1