netdev - RE: [PATCH V4 1/2] can: flexcan: fix deadlock when using self wakeup

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Date:   Fri, 25 Oct 2019 10:10:22 +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:     "wg@...ndegger.com" <wg@...ndegger.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "sean@...nix.com" <sean@...nix.com>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH V4 1/2] can: flexcan: fix deadlock when using self wakeup


Kindly Ping...

Best Regards,
Joakim Zhang

> -----Original Message-----
> From: Joakim Zhang <qiangqing.zhang@....com>
> Sent: 2019年10月9日 16:13
> To: mkl@...gutronix.de; linux-can@...r.kernel.org
> Cc: wg@...ndegger.com; netdev@...r.kernel.org; sean@...nix.com;
> dl-linux-imx <linux-imx@....com>; Joakim Zhang <qiangqing.zhang@....com>
> Subject: [PATCH V4 1/2] can: flexcan: fix deadlock when using self wakeup
> 
> As reproted by Sean Nyekjaer below:
> 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.
> 
> The best way to exit stop mode is in Wake Up interrupt context, and then
> suspend() and resume() functions can be symmetric. However, stop mode
> request and ack will be controlled by SCU(System Control Unit)
> firmware(manage clock,power,stop mode, etc. by Cortex-M4 core) in coming
> i.MX8(QM/QXP). And SCU firmware interface can't be available in interrupt
> context.
> 
> For compatibillity, the wake up mechanism can't be symmetric, so we need
> in_stop_mode hack.
> 
> Fixes: de3578c198c6 ("can: flexcan: add self wakeup support")
> Reported-by: Sean Nyekjaer <sean@...nix.com>
> Tested-by: Sean Nyekjaer <sean@...nix.com>
> Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
> 
> Changelog:
> V1->V2:
> 	* add Reported-by tag.
> 	* rebase on patch: can:flexcan:fix stop mode acknowledgment.
> V2->V3:
> 	* rebase on linux-can/testing.
> 	* change into patch set.
> V3->V4:
> 	* add Tested-by tag.
> ---
>  drivers/net/can/flexcan.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c index
> 1cd5179cb876..24cc386c4bce 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);
> @@ -1670,6 +1671,8 @@ static int __maybe_unused flexcan_suspend(struct
> device *device)
>  			err = flexcan_enter_stop_mode(priv);
>  			if (err)
>  				return err;
> +
> +			priv->in_stop_mode = true;
>  		} else {
>  			err = flexcan_chip_disable(priv);
>  			if (err)
> @@ -1696,6 +1699,15 @@ 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);
> +				err = flexcan_exit_stop_mode(priv);
> +				if (err)
> +					return err;
> +
> +				priv->in_stop_mode = false;
> +			}
> +
>  			disable_irq_wake(dev->irq);
>  		} else {
>  			err = pm_runtime_force_resume(device); @@ -1732,6 +1744,11
> @@ 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 to 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 it has enter
> +	 * the stop mode.
> +	 */
>  	if (netif_running(dev) && device_may_wakeup(device))
>  		flexcan_enable_wakeup_irq(priv, true);
> 
> @@ -1744,11 +1761,17 @@ static int __maybe_unused
> flexcan_noirq_resume(struct device *device)
>  	struct flexcan_priv *priv = netdev_priv(dev);
>  	int err;
> 
> +	/* Need to 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);
>  		err = flexcan_exit_stop_mode(priv);
>  		if (err)
>  			return err;
> +
> +		priv->in_stop_mode = false;
>  	}
> 
>  	return 0;
> --
> 2.17.1