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

[Guenter Roeck]

On 02/17/2017 07:16 AM, Alexandre Belloni wrote:
> 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@xxxxxxxxxxxxxxxxxx>
> > > ---
> > > 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.
You are correct. Sorry for the noise.

Seems odd that the watchdog must be _running_ to change the timeout.
Usually, if there is a restriction, it is the opposite. I hope this
doesn't cause race conditions, where the watchdog fires immediately
after being enabled due to a low timeout.

Guenter