linux-kernel - Re: [PATCH 0/3] ata port runtime power management support

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Message-ID: <CAOS58YMSwnp=Vm81+0_ZO9OYB4=NMnfETBen0QNCQwuDW0TjUA@mail.gmail.com>
Date:	Thu, 3 Nov 2011 07:30:15 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Lin Ming <ming.m.lin@...el.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Jeff Garzik <jgarzik@...ox.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	James Bottomley <JBottomley@...allels.com>,
	"Huang, Ying" <ying.huang@...el.com>,
	"Zhang, Rui" <rui.zhang@...el.com>
Subject: Re: [PATCH 0/3] ata port runtime power management support

Hello,

On Thu, Nov 3, 2011 at 7:21 AM, Lin Ming <ming.m.lin@...el.com> wrote:
>> * How much does this add on top of hardware timed auto spindown and
>>   dynamic link power management?
>
> Sorry, I don't understand this question.
> What do you mean?

I was curious about the amount of additional power saving on top of
the existing PM features.

>> * Do the added benefits justify yet another runtime powersaving
>>   mechanism?
>
> There will be ACPI firmware which supports ata port runtime D3Cold.
> To enable ata port runtime PM is the first step.

libata can already turn off unused ports although it wouldn't go as
far as putting the whole controller into D3.

>> * Any way we can tie the other stuff with overall runtime PM?
>
> What's the other stuff?
> Do you mean tie disk/link/port/controller stuff with overall runtime PM?

Hardware initiated spin-down (hdparm -S) and link power saving (look
for ata_lpm_*). It would be great if there's an overall design how
they interact before adding yet another PM vector.

Thanks.

-- 
tejun
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