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

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Date:	Fri, 3 Apr 2015 02:53:35 +0000
From:	"Fu, Borun" <borun.fu@...el.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Guenter Roeck <linux@...ck-us.net>
CC:	"linux-watchdog@...r.kernel.org" <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>,
	"Li, Aubrey" <aubrey.li@...el.com>
Subject: RE: [PATCH] PM / watchdog: iTCO: stop watchdog during system suspend

On Apr 3, 2015 06:04, Rafael J. Wysocki wrote:
> On Wednesday, April 01, 2015 06:21:40 PM Guenter Roeck wrote:
>> On 04/01/2015 05:31 PM, Rafael J. Wysocki wrote:
>>> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> [cut]
> 
>> Hi Rafael,
>> 
>> This only covers suspend and resume, but not any of the other
>> sleep operations (like SIMPLE_DEV_PM_OPS would do).
>> Is that intentional ?
> 
> Yes, it is:
>  (1) The problemm at hand is strictly specific to system suspend.
>  (2) The SIMPLE_DEV_PM_OPS etc macros don't cover the _noirq callback
> variants
>      (and we want to use the _noirq variants, because we want the
>      watchdog to be stopped as late and restarted as early as reasonably
>      possible). (3) I'm not even sure if adding runtime PM support to
>      this driver would make any sense. :-)
>> 
>>> +};
>>> +
>>> +#define ITCO_WDT_PM_OPS	&iTCO_wdt_pm
>> 
>> Checkpatch wants to see (&iTCO_wdt_pm).
>> 
>> ERROR: Macros with complex values should be enclosed in parentheses
> 
> Please find an updated patch below.
> 
> Rafael
> 
> 
Tested-by: Borun Fu <borun.fu@...el.com>

Borun
> ---
> 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>
> ---
>  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, 	}, };