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Date:   Fri, 17 May 2019 02:47:24 +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>
Subject: RE: [PATCH] can: flexcan: fix deadlock when using self wakeup


Hi Marc,

Sean Nyekjaer reported the issue, but the fix is incorrect.
https://www.spinics.net/lists/linux-can/msg01447.html

Could you help to add Sean Nyekjaer to this thread as I can't get the email address.
You can add the "Reported-by" tag if you pick up the patch.

Thanks a lot!

Best Regards,
Joakim Zhang

> -----Original Message-----
> From: Joakim Zhang
> Sent: 2019年5月17日 10:39
> To: mkl@...gutronix.de; linux-can@...r.kernel.org
> Cc: dl-linux-imx <linux-imx@....com>; wg@...ndegger.com;
> 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

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