Re: [patch 0/3] AHCI Link Power Management

[Arjan van de Ven <arjan@linux.intel.com>]

Jeff Garzik wrote:
> Arjan van de Ven wrote:
> > Tejun Heo wrote:
> > > Kristen Carlson Accardi wrote:
> > > > Hi,
> > > > This series of patches enables Aggressive Link Power Management for 
> > > > AHCI devices, as documented in the AHCI spec.  On my laptop (a 
> > > > Lenovo X60), this
> > > > saves me a full watt of power.  On other systems, reported power 
> > > > savings
> > > > range from .5-1.5 Watts.  It has been tested by the kind folks at 
> > > > #powertop
> > > > with similar results.  Please give it a try and let me know what you 
> > > > think.
> > >
> > > I'm not sure about this.  We need better PM framework to support
> > > powersaving in other controllers and some ahcis don't save much when
> > > only link power management is used, 
> >
> > do you have data to support this? The data we have from this patch is 
> > that it saves typically a Watt of power (depends on the machine of 
> > course, but the range is 0.5W to 1.5W). If you want to also have an 
> > even more agressive thing where you want to start disabling the entire 
> > controller... I don't see how this is in conflict with saving power on 
> > the link level by "just" enabling a hardware feature ....
>
> SATA standard defines lower power phy states.  So the same argument 
> you're using for AHCI applies there too -- "just" enabling an existing 
> hardware feature.
yes I'm not arguing against that. I was trying to find out (and 
suggest-unless-proven-otherwise) that the 2 are not exclusive or 
conflicting... in fact I assume both are wanted concurrently.
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