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

Pavel Machek
2008-02-26T21:49:08Z

On Tue 2008-02-26 10:52:36, Mark Lord wrote:
> 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.

Yep, I seen that, too. I'm just afraid to check, maybe AHCI powerdown
does not save that much power when links in powersave already...
Pavel
--
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