From 2ac8490412c98211750e5fde9b7a5cda3035d7fd Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Thu, 19 Aug 2021 11:57:04 +0200 Subject: watchdog: add gpio watchdog driver 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. Reviewed-by: Simon Glass Reviewed-by: Stefan Roese Signed-off-by: Rasmus Villemoes --- doc/device-tree-bindings/watchdog/gpio-wdt.txt | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) create mode 100644 doc/device-tree-bindings/watchdog/gpio-wdt.txt (limited to 'doc') diff --git a/doc/device-tree-bindings/watchdog/gpio-wdt.txt b/doc/device-tree-bindings/watchdog/gpio-wdt.txt new file mode 100644 index 0000000..c9a8559 --- /dev/null +++ b/doc/device-tree-bindings/watchdog/gpio-wdt.txt @@ -0,0 +1,19 @@ +GPIO watchdog timer + +Describes a simple watchdog timer which is reset by toggling a gpio. + +Required properties: + +- compatible: Must be "linux,wdt-gpio". +- gpios: gpio to toggle when wdt driver reset method is called. +- always-running: Boolean property indicating that the watchdog cannot + be disabled. At present, U-Boot only supports this kind of GPIO + watchdog. + +Example: + + gpio-wdt { + gpios = <&gpio0 1 0>; + compatible = "linux,wdt-gpio"; + always-running; + }; -- cgit v1.1