Hi Günter and Geert,
Catching up on the subject (because I was sleeping here in the US...)
On Friday, February 17, 2017, Geert Uytterhoeven wrote:
> > 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.
>
> I also thought 125ms was a bit short, but I'm happy to be proven wrong!
> Let's make a real watchdog driver instead ;-)
OK, I'll see about switching over to a real watchdog driver. As long as I
can get my reset handler, I'll be happy.
Besides, if I get the 8-bit counter register changed to 16-bit (a useful
WDT), then I already have a WDT made.
The good thing is that the DT binding will stay exactly the same, I just
need a new driver.
FWIW, if I was making a real product I would always have a WDT running (but
with a 1-3 second timeout just to make sure I was completely dead).
# side note, I tell people to set up a DMA with a timer trigger and
automatically feed the WDT that way, then they can set the DMA count to
whatever failsafe timeout they want. Not sure if I could submit that kind
of hackery in an upstream driver.
> >>> I know Geert's suggestion was in reference to saving power...but in
> >>> reality it's probably negligible when we are talking about 7.7us.
> >>> The reboot is going to automatically shut off all the peripherals
> >>> clocks as well.
> >>
> >> Maybe udelay(10); would have been more acceptable (and appropriate).
> >
> > Inside the while (1) loop? That's the same as a plain "while (1) ;"
> > ;-) Or just udelay(10) and return, with the latter never happening if
> > everything goes well? Then the next restart handler will be tried, if
> available.
> >
>
> That is what I meant. Or use udelay(20) to be on the safe side.
OK. Sounds like we agree on:
/* Start timer */
writew(WTCSR_MAGIC | WTSCR_WT | WTSCR_TME, base + WTCSR);
/* Wait for WDT overflow (reset) */
Udelay(20);
return NOTIFY_DONE;
}
FYI, I'll be at ELC next week, so I might not get to this until after then.
Thanks for the discussion.
Cheers
Chris
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