Re: [RFC] watchdog: renesas_wdt: don't keep timer value during suspend/resume

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On 12/7/18 1:45 PM, Wolfram Sang wrote:
Hi Guenter, all,

After discussing this mail thread [1] again, we concluded that giving
userspace enough time to prepare is our favourite option. So, do not
keep the time value when suspended but reset it when resuming.

[1] https://patchwork.kernel.org/patch/10252209/

Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>

Above exchange says it all, no need to repeat.

Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>

Thanks.

I can relate to the policy argument, though. Regardless of this patch, I
wonder if we can make it configurable from userspace. A draft:

#define	WDIOF_RESUME_OPTS	0x0800

#define	WDIOS_RESUME_KEEP	0x0008
#define	WDIOS_RESUME_RESET	0x0010

and then in watchdog_ioctl() under WDIOC_SETOPTIONS:

	if (!(wdd->info->options & WDIOF_RESUME_OPTS))
		err = -EOPNOTSUPP;
		goto break;

	if (val & WDIOS_RESUME_KEEP)
		wdd->status |= WDOG_KEEP_TIMER_WHEN_RESUME;

	if (val & WDIOS_RESUME_RESET)
		wdd->status ~= ~WDOG_KEEP_TIMER_WHEN_RESUME;

So, drivers with WDIOF_RESUME_OPTS could act on the
WDOG_KEEP_TIMER_WHEN_RESUME flag.

Opinions?


Not entirely sure I understand the use case.

Having said that, if we were to add this option, I think only a single
flag would be needed - WDIOF_RESUME_KEEP. All we need to do is declare
that a ping on resume shall be the default. Anything else would result
in undefined per-driver default behavior.

Guenter



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