[RFC 22/37] watchdog: renesas_wdt: Add restart support

[Fabrizio Castro]

Hello Guenter,

thank you for your feedback.

> Subject: Re: [RFC 22/37] watchdog: renesas_wdt: Add restart support
>
> On Thu, Jan 25, 2018 at 06:02:56PM +0000, Fabrizio Castro wrote:
> > This commit extends the driver to add restart support by implementing
> > the restart callback to trigger the watchdog as quickly as possible.
> >
> > Signed-off-by: Fabrizio Castro <fabrizio.castro at bp.renesas.com>
> > Signed-off-by: Ramesh Shanmugasundaram <ramesh.shanmugasundaram at bp.renesas.com>
> > ---
> >  drivers/watchdog/renesas_wdt.c | 19 +++++++++++++++++++
> >  1 file changed, 19 insertions(+)
> >
> > diff --git a/drivers/watchdog/renesas_wdt.c b/drivers/watchdog/renesas_wdt.c
> > index 831ef83..120ddac 100644
> > --- a/drivers/watchdog/renesas_wdt.c
> > +++ b/drivers/watchdog/renesas_wdt.c
> > @@ -107,6 +107,24 @@ static unsigned int rwdt_get_timeleft(struct watchdog_device *wdev)
> >  return DIV_BY_CLKS_PER_SEC(priv, 65536 - val);
> >  }
> >
> > +static int rwdt_restart(struct watchdog_device *wdev, unsigned long action,
> > +void *data)
> > +{
> > +struct rwdt_priv *priv = watchdog_get_drvdata(wdev);
> > +
> > +pm_runtime_get_sync(wdev->parent);
> > +
> > +rwdt_write(priv, 0x00, RWTCSRB);
> > +rwdt_write(priv, 0x00, RWTCSRA);
> > +rwdt_write(priv, 0xffff, RWTCNT);
> > +
> > +while (readb_relaxed(priv->base + RWTCSRA) & RWTCSRA_WRFLG)
> > +cpu_relax();
>
> Can this get stuck forever or should there be a timeout ?

This won't get stuck forever, the particular bit we are checking marks the period of time writing to register RWTCNT is prohibited due to synchronization from the previous write. It gets cleared eventually (quite quickly). Also, we use exactly the same logic for the "start" callback.

Best regards,
Fabrizio

>
> Guenter
>
> > +
> > +rwdt_write(priv, 0x80, RWTCSRA);
> > +return 0;
> > +}
> > +
> >  static const struct watchdog_info rwdt_ident = {
> >  .options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT,
> >  .identity = "Renesas WDT Watchdog",
> > @@ -118,6 +136,7 @@ static const struct watchdog_ops rwdt_ops = {
> >  .stop = rwdt_stop,
> >  .ping = rwdt_init_timeout,
> >  .get_timeleft = rwdt_get_timeleft,
> > +.restart = rwdt_restart,
> >  };
> >
> >  static int rwdt_probe(struct platform_device *pdev)
> > --
> > 2.7.4
> >
> > --
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