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

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Message-ID: <20080226214908.GC10280@elf.ucw.cz>
Date:	Tue, 26 Feb 2008 22:49:08 +0100
From:	Pavel Machek <pavel@....cz>
To:	Mark Lord <lkml@....ca>
Cc:	Mark Lord <liml@....ca>,
	kernel list <linux-kernel@...r.kernel.org>,
	Linux-pm mailing list <linux-pm@...ts.osdl.org>,
	stern@...land.harvard.edu, linux-ide@...r.kernel.org
Subject: Re: [ugly patch] Save .15W-.5W by AHCI powersaving

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
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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