linux-kernel - Re: [PATCH] ata: ahci: power off unused ports

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Date:	Sun, 01 Jun 2008 15:16:56 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Pavel Machek <pavel@....cz>
CC:	Kristen Carlson Accardi <kristen.c.accardi@...el.com>,
	Theodore Tso <tytso@....edu>, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ata: ahci: power off unused ports

Pavel Machek wrote:
> Hi!
> 
>>>> As far as I know the patch has gone nowhere.  I believe that 
>>>> Jeff wanted something more flexible than the module parameter that
>>>> I provided to override the BIOS options.  I am not working on this,
>>>> I figured he had a pretty firm idea what he wanted so he was better
>>>> equipped to write the patch.
>>> Thanks Kristen,
>>>
>>> Can you say which laptops you had tested this on where it saved power?
>>> (Did you test any Thinkpads, in particular?)  I'm wondering if it's
>>> worth trying to forward port your patch as a private mod to my kernel;
>>> 30 to 40 minutes of extra battery life is nothing to sneeze at!
>>>
>>> 						- Ted
>>>
>> I tested this on an Intel mobile software development platform 
>> with a newer mobile ICH - the power savings were measured at the actual 
>> component (via probes on the ICH), so I did not measure the power 
>> savings at the wall socket, although I would expect the power savings
>> to be even greater on the other side of the power supply.  So in short,
>> yes, I think it's worth it to give it a try - the patch is pretty
>> unintrusive, so it should be that difficult a port to do.
> 
> Can you repost the patch? I believe we should push it and only add
> complex enable/disable functionality if someone needs it...

If you are talking about SATA -- incorrect.

The patch deals with policy, and the user MUST have the ability to 
control this stuff.  Otherwise you create a situation where the user 
might be denied hotplug use in valid cases, or similar negative situations.

	Jeff



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