[0/6] watchdog: Add millisecond-level capabilities

Message

Corey Minyard June 20, 2020, 5:33 p.m. UTC

As mentioned before in the list, this is work for the ELISA (Linux in
safety critical systems) group.  Some use cases require tight watchdog
times so a system can recover quickly on a failure.

This patch series adds millisecond level capabilites that devices can
use if they wish, new ioctls to use those interfaces, new device
attributes with the higher precision, documentation, and it converts the
i6300 and softdog watchdog to use milliseconds.

All existing user APIs should work as before.  The interface between the
watchdog subsystem and the driver is converted to be modal.  If a flag
is set in the options then all interactions are in milliseconds.  If the
flag is not set then they are in seconds.

It's all pretty straightforward except for the calculations in the
i6300 driver, which required some thought.

Note that checkpatch gives warnings about there being no identifiers in
the function arguments in the watchdog ops structure, but I tried to
keep the style the same.

Thanks,

-corey