I put some debug statements in hwclock, and it told me that the CMOS
clock was _not_ in BCD mode. That one machine is a proliant 1600. Two
other proliant 1600''s I have were in BCD mode, as were a few other
linux
machines I had lying around.
I then hacked a bit further and had it write to the status register to
force it back into BCD mode.
And suddenly all is well again. It looks like Linux can handle a non-BCD
mode cmos clock in theory, but in practice something about it is
seriously broken.
James
> -----Original Message-----
> From: xen-devel-bounces@lists.xensource.com [mailto:xen-devel-
> bounces@lists.xensource.com] On Behalf Of James Harper
> Sent: Wednesday, 28 December 2005 16:34
> To: Ian Pratt; xen-devel@lists.xensource.com
> Subject: RE: [Xen-devel] more bizarre rtc behaviour...
>
> >
> > > I have now noticed that with the rtc module loaded it
> > > exhibits the behaviour I described, but if I unload the rtc
> > > module, it all works fine. The underlying hardware clock
> > > appears to be fine.
> >
> > The rtc module isn''t particularly useful in a xen
environment. Any
> idea
> > what in user space is using /dec/rtc ?
> >
>
> Nothing is loading it automatically, I just tried loading it as dom0
is> SMP, and the linux config recommends using rtc.ko in an SMP
environment.> I thought maybe that could be explaining my rtc kernel errors.
>
> It just occurred to me that the counting sequence appeared to be a
> mismatched BCD HEX problem.... something about rtc is forcing an
> interpretation of a HEX value as BCD (or maybe my bios is storing
> something as HEX that should be BCD?), eg:
>
> HEX | DEC | BCD
> 00 | 00 | 00
> 01 | 01 | 01
> ...............
> 08 | 08 | 08
> 09 | 09 | 09
> 0a | 10 | 00
> 0b | 11 | 11
> 0c | 12 | 12
> 0d | 13 | 13
> 0e | 14 | 14
> 0f | 15 | 15
> 10 | 16 | 10
> 11 | 17 | 11
> ...............
> 3a | 58 | 40
> 3b | 59 | 41
> 00 | 00 | 00
>
> Could Xen be responsible for that in any way?
>
> Thanks
>
> James
>
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