Re: [PATCH v2 3/3] watchdog: sama5d4: Implement resume hook

[Guenter Roeck]

On 02/17/2017 07:22 AM, Alexandre Belloni wrote:
> On 17/02/2017 at 06:47:03 -0800, Guenter Roeck wrote:
> > On 02/16/2017 11:30 AM, Alexandre Belloni wrote:
> > > When resuming for the deepest state on sama5d2, it is necessary to restore
> > > MR as the registers are lost.
> > >
> > > Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>
> > > ---
> > > Changes in v2:
> > >  - cache mr beofre suspending
> > >
> > >  drivers/watchdog/sama5d4_wdt.c | 32 ++++++++++++++++++++++++++++++++
> > >  1 file changed, 32 insertions(+)
> > >
> > > diff --git a/drivers/watchdog/sama5d4_wdt.c b/drivers/watchdog/sama5d4_wdt.c
> > > index 2a60251806d2..5ddeb4803dc3 100644
> > > --- a/drivers/watchdog/sama5d4_wdt.c
> > > +++ b/drivers/watchdog/sama5d4_wdt.c
> > > @@ -28,6 +28,7 @@
> > >  struct sama5d4_wdt {
> > >  	struct watchdog_device	wdd;
> > >  	void __iomem		*reg_base;
> > > +	u32			mr;
> >
> > Makes me wonder if we shouldn't just retain the original 'config'
> > (and maybe rename it to 'mr). After all, it _is_ used now.
> >
> > >  };
> > >
> > >  static int wdt_timeout = WDT_DEFAULT_TIMEOUT;
> > > @@ -248,11 +249,42 @@ static const struct of_device_id sama5d4_wdt_of_match[] = {
> > >  };
> > >  MODULE_DEVICE_TABLE(of, sama5d4_wdt_of_match);
> > >
> > > +#ifdef CONFIG_PM_SLEEP
> > > +static int sama5d4_wdt_suspend(struct device *dev)
> > > +{
> > > +	struct sama5d4_wdt *wdt = dev_get_drvdata(dev);
> > > +
> > > +	wdt->mr = wdt_read(wdt, AT91_WDT_MR);
> > > +
> >
> > Wouldn't you want to stop the watchdog here if it is running,
> > ie set AT91_WDT_WDDIS ?
>
> Some existing customers want the watchdog to continue to run while the
> system is suspended.
>
> > > +	return 0;
> > > +}
> > > +
> > > +static int sama5d4_wdt_resume(struct device *dev)
> > > +{
> > > +	struct sama5d4_wdt *wdt = dev_get_drvdata(dev);
> > > +	u32 reg;
> > > +
> > > +	reg = wdt_read(wdt, AT91_WDT_MR);
> > > +	if (reg & AT91_WDT_WDDIS)
> > > +		wdt_write(wdt, AT91_WDT_MR, reg & ~AT91_WDT_WDDIS);
> > > +
> > > +	wdt_write(wdt, AT91_WDT_MR, wdt->mr & ~AT91_WDT_WDDIS);
> >
> > Is that necessary ? Why not just write wdt->mr unconditionally ?
>
> Because you can change WDV and WDD *OR* WDDIS but not both at the same
> time.

Odd hardware ;-). Please add a comment explaining why the watchdog isn't
stopped on suspend, and why the AT91_WDT_MR has to be reprogrammed on resume.

Thanks,
Guenter