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>
Device Tree Bindings Staging Area
=================================
This directory contains device tree bindings for U-Boot.
These follow along with Linux kernel bindings, with a few additions. By
adding the files here, U-Boot patches can clearly show thees additions.
This makes it easier for device tree people to review these additions in
patches sent to the U-Boot mailing list.
The intent IS to commit these files to U-Boot. Hopefully at some point
the files will be stored in another repo (shared with Linux) which is
brought in as needed. Changes here are intended to mirror changes in the
Linux Documentation/devicetree/bindings/ directory.
sjg@chromium.org
17-Jan-12
2ac8490412