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authorRasmus Villemoes <rasmus.villemoes@prevas.dk>2021-08-19 11:57:04 +0200
committerStefan Roese <sr@denx.de>2021-08-31 12:04:03 +0200
commit2ac8490412c98211750e5fde9b7a5cda3035d7fd (patch)
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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 <sjg@chromium.org> Reviewed-by: Stefan Roese <sr@denx.de> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Diffstat (limited to 'doc')
-rw-r--r--doc/device-tree-bindings/watchdog/gpio-wdt.txt19
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diff --git a/doc/device-tree-bindings/watchdog/gpio-wdt.txt b/doc/device-tree-bindings/watchdog/gpio-wdt.txt
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+++ b/doc/device-tree-bindings/watchdog/gpio-wdt.txt
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+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;
+ };