Re: [PATCH] watchdog/hpwdt: Support Suspend and Resume

From: Guenter Roeck <linux@roeck-us.net>
To: Jerry Hoemann <jerry.hoemann@hpe.com>
Cc: wim@linux-watchdog.org, linux-watchdog@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] watchdog/hpwdt: Support Suspend and Resume
Date: Tue, 13 Feb 2024 08:12:57 -0800	[thread overview]
Message-ID: <7b70a8e7-10ce-4835-891c-b854919fa3cb@roeck-us.net> (raw)
In-Reply-To: <20240213070203.489846-1-jerry.hoemann@hpe.com>

On Tue, Feb 13, 2024 at 12:02:03AM -0700, Jerry Hoemann wrote:
> Add call backs to support suspend and resume.
> 

That makes me wonder if we should add something like
	watchdog_stop_on_suspend()
to the watchdog core. Almost every watchdog driver supporting
suspend/resume repeats the same sequence (except for the debug
message). That is a separate question, though.

> Signed-off-by: Jerry Hoemann <jerry.hoemann@hpe.com>
> ---
>  drivers/watchdog/hpwdt.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> diff --git a/drivers/watchdog/hpwdt.c b/drivers/watchdog/hpwdt.c
> index 138dc8d8ca3d..6565cfaa8e57 100644
> --- a/drivers/watchdog/hpwdt.c
> +++ b/drivers/watchdog/hpwdt.c
> @@ -378,11 +378,38 @@ static void hpwdt_exit(struct pci_dev *dev)
>  	pci_disable_device(dev);
>  }
>  
> +static int hpwdt_suspend(struct device *dev)
> +{
> +	dev_dbg(dev, "Suspend watchdog\n");
> +

Doesn't the suspend / resume code already display such debug messages ?

> +	if (watchdog_active(&hpwdt_dev))
> +		hpwdt_stop();
> +
> +	return 0;
> +}
> +
> +static int hpwdt_resume(struct device *dev)
> +{
> +	dev_dbg(dev, "Resume watchdog\n");
> +
> +	if (watchdog_active(&hpwdt_dev))
> +		hpwdt_start(&hpwdt_dev);
> +
> +	return 0;
> +}
> +
> +static DEFINE_SIMPLE_DEV_PM_OPS(hpwdt_pm_ops, hpwdt_suspend, hpwdt_resume);

That disables / enables the watchdog as part of regular suspend/resume
handling, meaning any hang during suspend/resume that happens later will
hang the system. Sure you don't want to use SET_LATE_SYSTEM_SLEEP_PM_OPS()
instead ?

Never mind, though. Your call, obviously.

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

Thanks,
Guenter