Re: [microblaze-uclinux] watchdog

[John Williams <john.williams@xxxxxxxxxxxxx>]

Hi Finn,

On Sun, Mar 22, 2009 at 9:51 AM, Finn Stadel Nielsen
<finnstadel@xxxxxxxxxx> wrote:

> Reading the xps_timebase_wdt datasheet closer... It seems this core is in
> fact rather useless for use as a timebase (unless you want a 1-minute
> timebase or you don't want to use the watch-dog or only use it in a
> complicated way).

Right.  Interrupts are generated only on 32-bit rollover, or watchdog
expiry, which is settable only as power-of-two clock cycles.  Not much
fun to use as a generic system timer.

On the subject of kernel timekeeping, in the upstream MicroBlaze arch
merge that Michal is currently managing, he's implemented some very
cool features of the kernel's timing/IRQ system - specifically the
NOHZ option, where no regular timer interrupts are generated at all -
the kernel just wakes up when there's some work to do.

> As a watch-dog timer alone I guess it's usable and it
> would be nice to have support for it in booth u-boot and linux.

The kernel has architecture for watchdog timers, it's a pretty simple
interface and a driver for the xps_timebase_wdt would be pretty
straight forward I expect.  Patches are welcome :)

> Triggering
> in the simple boot loader is not a problem, as it can't be configured to be
> active from cold boot, but has to be enabled first in software.

Probably a fairly small tweak on u-boot / microblaze arch.  Michal is
the microblaze maintainer for u-boot so I'm sure he'd welcome patches
on that too! :)

Cheers,

John
-- 
John Williams, PhD, B.Eng, B.IT
PetaLogix - Linux Solutions for a Reconfigurable World
w: www.petalogix.com  p: +61-7-30090663  f: +61-7-30090663
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