[PATCH] AHCI powersaving and port-stopping (2.6.22-rc4)

[Kristen Carlson Accardi]

On Mon, 11 Jun 2007 07:05:38 -0700
Arjan van de Ven <arjan at linux.intel.com> wrote:

> > This is very different from the patch I posted a while ago turning on
> > a few bits in the CMD register (ALPE and ASP) and which Intel is
> 
> we've not seen a patch that actually works in this area unfortunately. 
> We know Kristen's patch does work
> 
> > apparently now trying. That only saves around 250mW. Tejun's patch
> 
> .. and saves close to a watt on a laptop in our measurements
> 
> the patch is available on
> http://www.kernel.org/pub/linux/kernel/people/kristen/patches/SATA/alpm/
> 
> maybe worth a try as well..
> -

I've updated the hardware based patches and posted to the mailing list - 
they do indeed save anywhere from .6-1.5 watts depending on the system,
on my X60 they save about a watt.  I don't think that a hardware based
solution is irrelevant at all - it will usually be able to make faster
and more accurrate decisions about when to place the link into lower
power state than software could.

Note that the previous implementation that was posted didn't work for me,
so I just redid everything.

http://marc.info/?l=linux-kernel&m=118158780117084&w=2

Kristen