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

kathirav
2020-10-30T05:22:55Z

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?

> +}
> +
> 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?

> + 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;