linux-kernel - Re: [PATCH] watchdog: pnx4008: readout watchddog state

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Date:   Thu, 11 Apr 2019 18:13:39 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Vladimir Zapolskiy <vz@...ia.com>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Sylvain Lemieux <slemieux.tyco@...il.com>,
        Gregory Clement <gregory.clement@...tlin.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] watchdog: pnx4008: readout watchddog state

On 11/04/2019 09:03:05-0700, Guenter Roeck wrote:
> Hi Alexandre,
> 
> On Thu, Apr 11, 2019 at 05:36:46PM +0200, Alexandre Belloni wrote:
> > Readout the enabled state so it is possible to get the pre-userspace
> > handler working. Also, avoid disabling the watchdog when nowayout is set to
> > ensure the watchdog continues working and triggers if there is an issue
> > later in the boot or if userspace fails to start.
> > 
> > Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
> > ---
> >  drivers/watchdog/pnx4008_wdt.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/watchdog/pnx4008_wdt.c b/drivers/watchdog/pnx4008_wdt.c
> > index 8e261799c84e..9e3714e3814c 100644
> > --- a/drivers/watchdog/pnx4008_wdt.c
> > +++ b/drivers/watchdog/pnx4008_wdt.c
> > @@ -209,7 +209,11 @@ static int pnx4008_wdt_probe(struct platform_device *pdev)
> >  	watchdog_set_nowayout(&pnx4008_wdd, nowayout);
> >  	watchdog_set_restart_priority(&pnx4008_wdd, 128);
> >  
> > -	pnx4008_wdt_stop(&pnx4008_wdd);	/* disable for now */
> > +	if (readl(WDTIM_CTRL(wdt_base)) & COUNT_ENAB)
> > +		set_bit(WDOG_HW_RUNNING, &pnx4008_wdd.status);
> > +
> > +	if (!nowayout)
> > +		pnx4008_wdt_stop(&pnx4008_wdd);	/* disable for now */
> 
> I don't see the point of stopping the watchdog here, even though that is the
> old behavior. If it is possible to detect that the watchdog is running, we
> can let the core handle pings until the watchdog device is opened. The code
> above does that, but only if nowayout is set. That seems inconsistent and
> unnecessary. Is there a downside to doing that unconditionally ?
> 

I guess the downside is the change of behaviour. I don't think many will
be affected but they will have to ensure the core pings the watchdog
until the device is open.  WATCHDOG_HANDLE_BOOT_ENABLED is y by default
so that should be fine for most.

Honestly, I would just never disable the watchdog, that is the whole
point of this patch. If you are fine with that, I will just remove the
line.


> Nitpick: s/watchddog/watchdog/ in subject line.
> 

I'll fix it.


-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com