Re: [ugly patch] Save .15W-.5W by AHCI powersaving

[Mark Lord <lkml@rtr.ca>]

Pavel Machek wrote:
> Hi!
> 
>>> This is a patch (very ugly, assumes you have just one disk) to bring
>>> powersaving to AHCI. You need Alan's SCSI autosuspend (attached) patch
>>> as a base.
>>>
>>> It saves .5W compared to config with disk spinning, and even .15W
>>> compared to hdparm -y... on my thinkpad x60 anyway.
>> ..
>>
>> There was a discussion of this here today.
> 
> Real-life discussion, or something I could read? :-).
> 
>> It makes good use of AHCI-specific features.
>>
>> Has it been tested with a Port-Multiplier yet?
> 
> I do not know what port-multiplier is, sorry. But it was not really
> tested. It is not expected to work on any other config than notebook
> very similar to mine.
> 
>> This is cool enough that we really ought to do a hardware-independent
>> version, so that all SATA interfaces could benefit.  Especially ata_piix,
>> but others too.
> 
> Well, it seems like it is 10 lines per driver once Alan's SCSI
> autosuspend patches are in...
..

Cool (literally)!

I think I might have gotten your patch confused in my mind
with another AHCI patch, which uses features of the chip itself
to automatically negotiate/change link power status on the fly
(no s/w needed, other than to turn it on).

That one is very ACPI specific, though.