AM335x: How to implement WD Timer reboot after kernel crash

The WDT must be enabled before the kernel crash, then it will reset the processor automatically.

Hi,

the watchdog can be controlled by writing to device file /dev/watchdog.
Basically the watchdog timer is activated when /dev/watchdog is opened by user space and will reboot the board
unless the watchdog is notified within a certain time that system is "alive" by writing some data to the file.
For example command:

echo 'c' > /dev/watchdog

will activate the watchdog and there will be reset after 60 seconds unless new echo to this file is issued
within this period.
The watchdog can be disabled by command:

echo 'V' > /dev/watchdog

and then there will be no reset after that. Note that in this command 'V' (capital v) is a magic character,
recognized by the driver, while 'c' that I used in first command was just random data (can be any other letter).

You can get more detailed info how to interact with the watchdog and use /dev/watchdog file in
<kernel dir>/Documentation/watchdog/watchdog-api.txt. Also there is some example code in
<kernel dir>/Documentation/watchdog/src directory.
(also there is described more flexible ioctl interface to /dev/watchdog that can be used instead of writes)

Regards,
Yordan

Hi,

it seems that in the version of the kernel that you use there is no support for "magic close" feature:
e2e.ti.com/.../449118

However for experiment in the file "<kernel>/drivers/watchdog/omap_wdt.c" you can try to change the line:
.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
to
.options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
in the definition of struct "omap_wdt_info" and see if that works as expected.
(Note that omap_wdt is usually set as module, so you need to rebuild and install modules, not just the kernel)

Regards,
Yordan