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SubjectRE: [PATCH 2/3] watchdog: da9063: Use pre configured timeout when watchdog is running
Date
On 26 March 2020 15:02, Stefan Riedmueller wrote:

> If the watchdog is already running during probe use its pre-configured
> timeout instead of a default timeout to make sure the watchdog is pinged
> in time until userspace takes over.

At least for this driver I don't think there's an issue here with regards to
not pinging in time. Calling 'da9063_wdt_update_timeout()', as it currently
does in the probe() when the watchdog is already active, actually disables the
watchdog before then setting a new timeout value, so by that method we're
avoiding a timeout and starting a new timer period.

To my mind the timeout value should come from DT if possible, which I would
assume for the most part would match whatever is defined in the bootloader as
well, unless I'm mistaken. If that's not available though then I would maybe
agree on falling back to a value that was already programmed in the bootloader
rather than the driver default which should be the last resort.

>
> Signed-off-by: Stefan Riedmueller <s.riedmueller@phytec.de>
> ---
> drivers/watchdog/da9063_wdt.c | 29 ++++++++++++++++++-----------
> 1 file changed, 18 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/watchdog/da9063_wdt.c b/drivers/watchdog/da9063_wdt.c
> index 3d65e92a4e3f..34d0c4f03814 100644
> --- a/drivers/watchdog/da9063_wdt.c
> +++ b/drivers/watchdog/da9063_wdt.c
> @@ -46,15 +46,16 @@ static unsigned int da9063_wdt_timeout_to_sel(unsigned
> int secs)
> }
>
> /*
> - * Return 0 if watchdog is disabled, else non zero.
> + * Read the currently active timeout.
> + * Zero means the watchdog is disabled.
> */
> -static unsigned int da9063_wdt_is_running(struct da9063 *da9063)
> +static unsigned int da9063_wdt_read_timeout(struct da9063 *da9063)
> {
> unsigned int val;
>
> regmap_read(da9063->regmap, DA9063_REG_CONTROL_D, &val);
>
> - return val & DA9063_TWDSCALE_MASK;
> + return wdt_timeout[val & DA9063_TWDSCALE_MASK];
> }
>
> static int da9063_wdt_disable_timer(struct da9063 *da9063)
> @@ -191,6 +192,7 @@ static int da9063_wdt_probe(struct platform_device
> *pdev)
> struct device *dev = &pdev->dev;
> struct da9063 *da9063;
> struct watchdog_device *wdd;
> + int timeout;
>
> if (!dev->parent)
> return -EINVAL;
> @@ -214,15 +216,20 @@ static int da9063_wdt_probe(struct platform_device
> *pdev)
> watchdog_set_restart_priority(wdd, 128);
> watchdog_set_drvdata(wdd, da9063);
>
> - /* Set default timeout, maybe override it with DT value, scale it */
> - wdd->timeout = DA9063_WDG_TIMEOUT;
> - watchdog_init_timeout(wdd, 0, dev);
> - da9063_wdt_set_timeout(wdd, wdd->timeout);
> -
> - /* Change the timeout to the default value if the watchdog is running */
> - if (da9063_wdt_is_running(da9063)) {
> - da9063_wdt_update_timeout(da9063, wdd->timeout);
> + /*
> + * Use pre-configured timeout if watchdog is already running.
> + * Otherwise set default timeout, maybe override it with DT value,
> + * scale it
> + */
> + timeout = da9063_wdt_read_timeout(da9063);
> + if (timeout) {
> + wdd->timeout = timeout;
> set_bit(WDOG_HW_RUNNING, &wdd->status);
> + dev_info(da9063->dev, "watchdog is running (%u s)", timeout);
> + } else {
> + wdd->timeout = DA9063_WDG_TIMEOUT;
> + watchdog_init_timeout(wdd, 0, dev);
> + da9063_wdt_set_timeout(wdd, wdd->timeout);
> }
>
> return devm_watchdog_register_device(dev, wdd);
> --
> 2.23.0

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