linux-kernel - Re: [PATCH] PM / watchdog: iTCO: stop watchdog during system suspend

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Message-ID: <551E29B7.7050801@roeck-us.net>
Date:	Thu, 02 Apr 2015 22:48:39 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	linux-watchdog@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Wim Van Sebroeck <wim@...ana.be>,
	Aubrey Li <aubrey.li@...el.com>, Borun Fu <borun.fu@...el.com>
Subject: Re: [PATCH] PM / watchdog: iTCO: stop watchdog during system suspend

On 04/02/2015 03:04 PM, Rafael J. Wysocki wrote:
[ ... ]
>
> ---
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Subject: PM / watchdog: iTCO: stop watchdog during system suspend
>
> If the target sleep state of the system is not an ACPI sleep state
> (S1, S2 or S3), the TCO watchdog needs to be stopped during system
> suspend, because it may not be possible to ping it any more after
> timekeeping has been suspended (suspend-to-idle does that for
> one example).
>
> For this reason, provide ->suspend_noirq and ->resume_noirq
> callbacks for the iTCO watchdog driver and use them to stop
> and restart the watchdog during system suspend and resume,
> respectively, if the system is not going to enter an ACPI
> sleep state (in which case the watchdog will be stopped
> by the platform firmware before the state is entered).
>
> Reported-by: Borun Fu <borun.fu@...el.com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
>   drivers/watchdog/iTCO_wdt.c |   51 ++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 51 insertions(+)
>
> Index: linux-pm/drivers/watchdog/iTCO_wdt.c
> ===================================================================
> --- linux-pm.orig/drivers/watchdog/iTCO_wdt.c
> +++ linux-pm/drivers/watchdog/iTCO_wdt.c
> @@ -51,6 +51,7 @@
>   #define DRV_VERSION	"1.11"
>
>   /* Includes */
> +#include <linux/acpi.h>			/* For ACPI support */
>   #include <linux/module.h>		/* For module specific items */
>   #include <linux/moduleparam.h>		/* For new moduleparam's */
>   #include <linux/types.h>		/* For standard types (like size_t) */
> @@ -103,6 +104,8 @@ static struct {		/* this is private data
>   	struct platform_device *dev;
>   	/* the PCI-device */
>   	struct pci_dev *pdev;
> +	/* whether or not the watchdog has been suspended */
> +	bool suspended;
>   } iTCO_wdt_private;
>
>   /* module parameters */
> @@ -571,12 +574,60 @@ static void iTCO_wdt_shutdown(struct pla
>   	iTCO_wdt_stop(NULL);
>   }
>
> +#ifdef CONFIG_PM_SLEEP
> +/*
> + * Suspend-to-idle requires this, because it stops the ticks and timekeeping, so
> + * the watchdog cannot be pinged while in that state.  In ACPI sleep states the
> + * watchdog is stopped by the platform firmware.
> + */
> +
> +#ifdef CONFIG_ACPI
> +static inline bool need_suspend(void)
> +{
> +	return acpi_target_system_state() == ACPI_STATE_S0;
> +}
> +#else
> +static inline bool need_suspend(void) { return true; }
> +#endif
> +
> +static int iTCO_wdt_suspend_noirq(struct device *dev)
> +{
> +	int ret = 0;
> +
> +	iTCO_wdt_private.suspended = false;
> +	if (watchdog_active(&iTCO_wdt_watchdog_dev) && need_suspend()) {
> +		ret = iTCO_wdt_stop(&iTCO_wdt_watchdog_dev);
> +		if (!ret)
> +			iTCO_wdt_private.suspended = true;
> +	}
> +	return ret;
> +}
> +
> +static int iTCO_wdt_resume_noirq(struct device *dev)
> +{
> +	if (iTCO_wdt_private.suspended)
> +		iTCO_wdt_start(&iTCO_wdt_watchdog_dev);
> +
> +	return 0;
> +}
> +
> +struct dev_pm_ops iTCO_wdt_pm = {
> +	.suspend_noirq = iTCO_wdt_suspend_noirq,
> +	.resume_noirq = iTCO_wdt_resume_noirq,
> +};
> +
> +#define ITCO_WDT_PM_OPS	(&iTCO_wdt_pm)
> +#else
> +#define ITCO_WDT_PM_OPS	NULL
> +#endif /* CONFIG_PM_SLEEP */
> +
>   static struct platform_driver iTCO_wdt_driver = {
>   	.probe          = iTCO_wdt_probe,
>   	.remove         = iTCO_wdt_remove,
>   	.shutdown       = iTCO_wdt_shutdown,
>   	.driver         = {
>   		.name   = DRV_NAME,
> +		.pm     = ITCO_WDT_PM_OPS,
>   	},
>   };
>
>
> --
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