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

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Date:	Thu, 14 Jun 2007 16:56:43 +0900
From:	Tejun Heo <htejun@...il.com>
To:	Kristen Carlson Accardi <kristen.c.accardi@...el.com>
CC:	Pavel Machek <pavel@....cz>,
	Arjan van de Ven <arjan@...ux.intel.com>, jeff@...zik.org,
	james.bottomley@...eleye.com, linux-ide@...r.kernel.org,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jens Axboe <jens.axboe@...cle.com>
Subject: Re: [patch 0/3] AHCI Link Power Management

Kristen Carlson Accardi wrote:
>>>>> 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?
>>> Yeah, it was some Lenovo notebook.  Pavel is more familiar with the
>>> hardware.  Pavel, what was the notebook which didn't save much power
>>> with standard SATA power save but needed port to be completely turned off?
>> Thinkpad x60. Some one Kristen probably used while developing the
>> patch :-).
> 
> Yes - that confirms my conclusion that the first patch just wasn't
> done correctly - cause when I measure the power savings with a power
> meter on the X60 with my patches I see ~ 1W.

Hmmm... Could it be that the controller doesn't enter powersave state
when SControl is written to?

-- 
tejun
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