Re: [PATCH] amd76x_pm: C3 powersaving for AMD K7

[Erik Slagter <erik@slagter.name>]

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On Tue, 2006-01-31 at 19:34 -0800, Andrew Morton wrote:
> > This is a processor idle module for AMD SMP 760MP(X) based systems.
> >  The patch was originally written by Tony Lindgren and has been around
> >  since 2002.  It enables C2 mode on AMD SMP systems and thus saves
> >  about 70 - 90 W of energy in the idle mode compared to the default idle
> >  mode.  The idle function has been rewritten and is now free of locking
> >  issues and is independent from the number of CPUs.  The impact
> >  from this module on the system clock and on i/o transfer are now fairly
> >  low.

Very nice, but I do have problems with it (last tested version about a
month ago).

I have a Tyan S2466 (760/8MPX) motherboard with a Promise PDC20575
(SATAII150 TX2plus), with two disks configured as raid-1. As soon as C2
starts to kick in (or C3 that doesn't matter) my syslog/dmesg starts to
fill up with error messages from the attached disks and one of the two
(at random) disks is kicked out of the raid. It looks like the other
disk keeps functioning although it keeps spewing lots of error messages.

To me it looks like the Promise controller goes totally bunkus when one
single interrupt is not served, or when it cannot bus master within a
certain time interval. I have tried to work around this problem by using
_very_ conservative values for the irq-watcher. This works well for some
time, but sooner or later the problem re-appears.

So it looks like the only way is to tackle the source of the problem. I
already reported this on linux-ide, but no response. I assume they think
it's a amd76x_pm specific issue.

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