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Re: watchdog - powerpc
- From: Bob Koninckx <bob dot koninckx at mech dot kuleuven dot ac dot be>
- To: Jonathan Larmour <jifl at eCosCentric dot com>
- Cc: ecos-discuss at sources dot redhat dot com
- Date: 23 May 2003 09:28:51 +0200
- Subject: Re: [ECOS] watchdog - powerpc
- Organization: KULeuven
- References: <1053378740.1367.6.camel@pc-002> <3ECD7BF3.40304@eCosCentric.com>
On Fri, 2003-05-23 at 03:40, Jonathan Larmour wrote:
> Bob Koninckx wrote:
> > Powerpc _enables_ the watchdog by default. According to the hardware
> > manual you can only disable it out of reset but never re-enable it
> > afterwards.
> >
> > from the spec ... SYPCR
> >
> > This register can be read at any time but can be written only once after
> > system reset ...
> >
> > I do not think you want a watchdog in redboot. But then redboot needs to
> > disable it, meaning you can not use it in the application afterwards
> > either. On the other hand, leaving it enabled in redboot gives the
> > application a chance to decide. But then you'll end up having problems
> > in redboot if you do not start the application fast enough. Am I missing
> > something ?
>
> Have the HAL provide a default NO-OP watchdog exception handler that acks
> the watchdog (or whatever's required)? An application or watchdog device
> driver can then override as required just by overriding the exception.
mmm ... Not really an option. You can indeed choose between either a
reset of the board or an interrupt upon watchdog timeout. But if you go
for the interrupt, there's no way of changing it to reset afterwards.
And I want the reset! Damn write once register :-(
Can you make use of interrupts in redboot? I tought they're all
disabled?
>
> Or arguably just write a standard watchdog device driver (as lives in
> devs/watchdog and uses io/watchdog) and include it in the RedBoot
> image.... and if CYGPKG_IO_WATCHDOG isn't defined in <pkgconf/system.h>
> just disable the watchdog entirely in SYPCR.
That's what I planned to do. I was just looking for a way to avoid this
kind of coupling between redboot and the application. Because of the
write-once nature of the SYPCR register and the watchdog being enabled
by default, redboot and the application can not decide independently on
the use of a watchdog.
Thanks,
Bob
>
> Jifl
> --
> eCosCentric http://www.eCosCentric.com/ The eCos and RedBoot experts
> --[ "You can complain because roses have thorns, or you ]--
> --[ can rejoice because thorns have roses." -Lincoln ]-- Opinions==mine
--
----------------------------------------------------------------------
ir. Bob Koninckx
Katholieke Universiteit Leuven
Division Production Engineering, tel. +32 16 322535
Machine Design and Automation fax. +32 16 322987
Celestijnenlaan 300B bob.koninckx@mech.kuleuven.ac.be
B-3001 Leuven Belgium http://www.mech.kuleuven.ac.be/pma
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