Re: [PATCH v2] watchdog: qcom_wdt: set WDOG_HW_RUNNING bit when appropriate

Robert Marko
2020-10-31T12:13:07Z

On Fri, Oct 30, 2020 at 6:21 AM <kathirav@codeaurora.org> wrote:
>
> On 2020-10-28 17:16, Robert Marko wrote:
> > If the watchdog hardware is enabled/running during boot, e.g.
> > due to a boot loader configuring it, we must tell the
> > watchdog framework about this fact so that it can ping the
> > watchdog until userspace opens the device and takes over
> > control.
> >
> > Do so using the WDOG_HW_RUNNING flag that exists for exactly
> > that use-case.
> >
> > Given the watchdog driver core doesn't know what timeout was
> > originally set by whoever started the watchdog (boot loader),
> > we make sure to update the timeout in the hardware according
> > to what the watchdog core thinks it is.
> >
> > Signed-off-by: Robert Marko <robert.marko@sartura.hr>
> > Cc: Luka Perkov <luka.perkov@sartura.hr>
> > ---
> > Changes in v2:
> > * Correct authorship
> >
> > drivers/watchdog/qcom-wdt.c | 22 ++++++++++++++++++++++
> > 1 file changed, 22 insertions(+)
> >
> > diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
> > index ab7465d186fd..28c93a918e38 100644
> > --- a/drivers/watchdog/qcom-wdt.c
> > +++ b/drivers/watchdog/qcom-wdt.c
> > @@ -152,6 +152,13 @@ static int qcom_wdt_restart(struct
> > watchdog_device *wdd, unsigned long action,
> > return 0;
> > }
> >
> > +static int qcom_wdt_is_running(struct watchdog_device *wdd)
> > +{
> > + struct qcom_wdt *wdt = to_qcom_wdt(wdd);
> > +
> > + return (readl(wdt_addr(wdt, WDT_EN)) & 1);
>
> QCOM_WDT_ENABLE macro can be used instead of 1?
Yes, pushed this in v4(Forgot to do it in v3).
Thanks
>
> > +}
> > +
> > static const struct watchdog_ops qcom_wdt_ops = {
> > .start = qcom_wdt_start,
> > .stop = qcom_wdt_stop,
> > @@ -294,6 +301,21 @@ static int qcom_wdt_probe(struct platform_device
> > *pdev)
> > wdt->wdd.timeout = min(wdt->wdd.max_timeout, 30U);
> > watchdog_init_timeout(&wdt->wdd, 0, dev);
> >
> > + if (qcom_wdt_is_running(&wdt->wdd)) {
> > + /*
> > + * Make sure to apply timeout from watchdog core, taking
> > + * the prescaler of this driver here into account (the
> > + * boot loader might be using a different prescaler).
> > + *
> > + * To avoid spurious resets because of different scaling,
> > + * we first disable the watchdog, set the new prescaler
> > + * and timeout, and then re-enable the watchdog.
> > + */
> > + qcom_wdt_stop(&wdt->wdd);
>
> qcom_wdt_start disables the WDT, configure the timeout values and
> enables it. Do we still need to call qcom_wdt_stop?
No, as the start will actually stop the WDT and then set everything up.
Pushed in v3.
>
> > + qcom_wdt_start(&wdt->wdd);
> > + set_bit(WDOG_HW_RUNNING, &wdt->wdd.status);
> > + }
> > +
> > ret = devm_watchdog_register_device(dev, &wdt->wdd);
> > if (ret)
> > return ret;