On Wed, Feb 22, 2017 at 01:35:12PM +0000, Chris Brandt wrote:

Hello Geert and Guenter,

On Thursday, February 16, 2017, Guenter Roeck wrote:

quoted

FWIW, the watchdog subsystem should support that easily, even with 125 ms
hardware timeout. We added that capability for that very purpose. That
would only fail if the system is stuck with interrupts disabled for more
than 125 ms, which seems unlikely. I think the gpio watchdog on some
systems has a similar low hardware timeout.

While I'm going to try that for the RZ/A1, I have a question for you guys
(or anyone else that has an opinion about end applications)


If I were going to make a request to the chip designers to make the timeout longer
for the next RZ/A chip, what would be a good max timeout for common Linux applications?

Looking through the drivers in the watchdog directly, I see default timeouts of 20,
30, 60, and 120 seconds.

30 and 60 are pretty common for default timeouts, though I personally think
they are a bit long. If you want direct HW support, a maximum of 120 seconds
should be sufficient though not really necessary anymore since the core
supports virtual timeouts. A maximum of at least 30 seconds would be needed
if the watchdog is supposed to run at boot time (ie if it is enabled by
ROMMON/BIOS and kept running by the kernel).

Hope this helps,
Guenter