linux-kernel - Re: [PATCH v2 2/3] watchdog: sama5d4: Fix setting timeout when watchdog is disabled

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Date:   Fri, 17 Feb 2017 16:16:50 +0100
From:   Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Wim Van Sebroeck <wim@...ana.be>,
        Nicolas Ferre <nicolas.ferre@...el.com>,
        linux-watchdog@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] watchdog: sama5d4: Fix setting timeout when
 watchdog is disabled

On 17/02/2017 at 06:40:33 -0800, Guenter Roeck wrote:
> On 02/16/2017 11:30 AM, Alexandre Belloni wrote:
> > The datasheet states: "When setting the WDDIS bit, and while it is set, the
> > fields WDV and WDD must not be modified."
> > 
> > Ensure WDDIS is not set when changing the timeout and set it afterwards if
> > the watchdog was disabled.
> > 
> > Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
> > ---
> > Changes in v2:
> >  - new patch
> >  drivers/watchdog/sama5d4_wdt.c | 9 ++++++++-
> >  1 file changed, 8 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/watchdog/sama5d4_wdt.c b/drivers/watchdog/sama5d4_wdt.c
> > index 2c6f5a70ae67..2a60251806d2 100644
> > --- a/drivers/watchdog/sama5d4_wdt.c
> > +++ b/drivers/watchdog/sama5d4_wdt.c
> > @@ -90,11 +90,18 @@ static int sama5d4_wdt_set_timeout(struct watchdog_device *wdd,
> >  	u32 reg;
> > 
> >  	reg = wdt_read(wdt, AT91_WDT_MR);
> > +
> > +	if (reg & AT91_WDT_WDDIS)
> > +		wdt_write(wdt, AT91_WDT_MR, reg & ~AT91_WDT_WDDIS);
> > +
> >  	reg &= ~AT91_WDT_WDV;
> >  	reg &= ~AT91_WDT_WDD;
> >  	reg |= AT91_WDT_SET_WDV(value);
> >  	reg |= AT91_WDT_SET_WDD(value);
> > -	wdt_write(wdt, AT91_WDT_MR, reg);
> > +	wdt_write(wdt, AT91_WDT_MR, reg & ~AT91_WDT_WDDIS);
> > +
> > +	if (reg & AT91_WDT_WDDIS)
> > +		wdt_write(wdt, AT91_WDT_MR, reg);
> > 
> That means if the watchdog is running, the timeout would not be updated.
> It should be updated no matter if it is running or not.
> 

No, it is enabling the watchdog, then changing WDV and WDD and finally
disabling the watchdog if necessary. So, WDV and WDD are always changed.

-- 
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com