[PATCH v2 08/10] watchdog: add gpio watchdog driver

[Simon Glass]

On Thu, 27 May 2021 at 16:00, Rasmus Villemoes
<rasmus.villemoes at prevas.dk> wrote:
>
> A rather common kind of external watchdog circuit is one that is kept
> alive by toggling a gpio. Add a driver for handling such a watchdog.
>
> The corresponding linux driver apparently has support for some
> watchdog circuits which can be disabled by tri-stating the gpio, but I
> have never actually encountered such a chip in the wild; the whole
> point of adding an external watchdog is usually that it is not in any
> way under software control. For forward-compatibility, and to make DT
> describe the hardware, the current driver only supports devices that
> have the always-running property. I went a little back and forth on
> whether I should fail ->probe or only ->start, and ended up deciding
> ->start was the right place.
>
> The compatible string is probably a little odd as it has nothing to do
> with linux per se - however, I chose that to make .dts snippets
> reusable between device trees used with U-Boot and linux, and this is
> the (only) compatible string that linux' corresponding driver and DT
> binding accepts. I have asked whether one should/could add "wdt-gpio"
> to that binding, but the answer was no:
>
>   https://lore.kernel.org/lkml/CAL_JsqKEGaFpiFV_oAtE+S_bnHkg4qry+bhx2EDs=NSbVf_giA@mail.gmail.com/
>
> If someone feels strongly about this, I can certainly remove the
> "linux," part from the string - it probably wouldn't the only place where
> one can't reuse a DT snippet as-is between linux and U-Boot.
>
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes at prevas.dk>
> ---
>  .../watchdog/gpio-wdt.txt                     | 19 +++++
>  drivers/watchdog/Kconfig                      |  9 +++
>  drivers/watchdog/Makefile                     |  1 +
>  drivers/watchdog/gpio_wdt.c                   | 69 +++++++++++++++++++
>  4 files changed, 98 insertions(+)
>  create mode 100644 doc/device-tree-bindings/watchdog/gpio-wdt.txt
>  create mode 100644 drivers/watchdog/gpio_wdt.c
>

Reviewed-by: Simon Glass <sjg at chromium.org>