Re: [PATCH v3 2/4] watchdog: da9062: reset board on watchdog timeout

[Christoph Niedermaier <cniedermaier@dh-electronics.com>]

From: Andrej Picej
Sent: Wednesday, December 1, 2021 9:15 AM
> Implement a method to change watchdog timeout configuration based on DT
> binding ("dlg,wdt-sd"). There is a possibility to change the bahaviour
> of watchdog reset. Setting WATCHDOG_SD bit enables SHUTDOWN mode, and
> clearing it enables POWERDOWN mode on watchdog timeout.
> 
> If no DT binding is specified the WATCHDOG_SD bit stays in default
> configuration, not breaking behaviour of devices which might depend on
> default fuse configuration.
> 
> Note: This patch requires that the config register CONFIG_I is
> configured as writable in the da9062 multi function device.
> 
> Signed-off-by: Andrej Picej <andrej.picej@norik.com>
> ---
> Changes in v3:
>  - no changes
> 
> Changes in v2:
>  - don't force the "reset" for all da9062-watchdog users, instead add DT
>    binding where the behavior can be selected
> ---
>  drivers/watchdog/da9062_wdt.c | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/drivers/watchdog/da9062_wdt.c b/drivers/watchdog/da9062_wdt.c
> index f02cbd530538..e342e9e50cb1 100644
> --- a/drivers/watchdog/da9062_wdt.c
> +++ b/drivers/watchdog/da9062_wdt.c
> @@ -85,8 +85,33 @@ static int da9062_wdt_start(struct watchdog_device *wdd)
>  {
>         struct da9062_watchdog *wdt = watchdog_get_drvdata(wdd);
>         unsigned int selector;
> +       unsigned int mask;
> +       u32 val;
>         int ret;
> 
> +       /* Configure what happens on watchdog timeout. Can be specified with
> +        * "dlg,wdt-sd" dt-binding (0 -> POWERDOWN, 1 -> SHUTDOWN).
> +        * If "dlg,wdt-sd" dt-binding is NOT set use the default.
> +        */
> +       ret = device_property_read_u32(wdd->parent, "dlg,wdt-sd", &val);
> +       if (!ret) {
> +               if (val)
> +                       /* Use da9062's SHUTDOWN mode */
> +                       mask = DA9062AA_WATCHDOG_SD_MASK;
> +               else
> +                       /* Use da9062's POWERDOWN mode. */
> +                       mask = 0x0;
> +
> +               ret = regmap_update_bits(wdt->hw->regmap,
> +                                               DA9062AA_CONFIG_I,
> +                                               DA9062AA_WATCHDOG_SD_MASK,
> +                                               mask);
> +
> +               if (ret)
> +                       dev_err(wdt->hw->dev, "failed to set wdt reset mode:
> %d\n",
> +                               ret);
> +       }
> +
>         selector = da9062_wdt_timeout_to_sel(wdt->wdtdev.timeout);
>         ret = da9062_wdt_update_timeout_register(wdt, selector);
>         if (ret)
> --
> 2.25.1
>

I have a question how to correctly restart the system after
watchdog timeout.
If I understand it correct after watchdog timeout the system
restarts only if WATCHDOG_SD (Bit 3) in register CONFIG_I is
set.
What is the difference if WATCHDOG_SD isn't set, but WAKE_UP
(Bit 2) in register CONTROL_F is set? From outside on my
system I observe the same behavior. After watchdog timeout
my system restarts. So where are the differences?
It would be nice if you could answer this question, as you
certainly know this chip very well.

Regards
Christoph
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