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

[Joerg Sommrey <jo@sommrey.de>]

On Thu, Feb 02, 2006 at 02:37:25PM -0800, Andrew Morton wrote:
> Joerg Sommrey <jo@sommrey.de> wrote:
> >
> > This is a processor idle module for AMD SMP 760MP(X) based systems.
> >
> 
> Len's comments about loss of cache coherency on some machines possibly
> causing corruption made me drop this patch.   Was I wrong to do so?
> 
You maintain -mm, so it's your decision.  I don't think it is a question
of right or wrong.  If you regard this stuff as too risky, dropping
it is ok.

However, I disagree with Len in two points:
- I cannot see a problem witch cache snooping.  The AMD-768 docs clearly
  states that trying to snoop the cache while in C3 is a resume event.
- Enabling C2/C3 in the BIOS would be a very bad thing IMHO.  From all
  the testing with amd76x_pm I found that is very tricky to go into
  C2/C3 "the right way".  Simply reading the PM register without a
  suitable logic around leads to all kinds of instabilities.  You need
  to implement this logic and then enable the hardware.  The BIOS cannot
  do this.

-jo

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-rw-r--r--  1 jo users 63 2006-02-03 07:43 /home/jo/.signature