linux-kernel - Re: [PATCH v2 0/4] ata port runtime power management support

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Message-ID: <20111110153036.GC27258@google.com>
Date:	Thu, 10 Nov 2011 07:30:36 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Lin Ming <ming.m.lin@...el.com>
Cc:	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	linux-scsi@...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>,
	Kay Sievers <kay.sievers@...y.org>
Subject: Re: [PATCH v2 0/4] ata port runtime power management support

Hello,

(cc'ing Kay for the sysfs tree hierarchy change)

On Thu, Nov 10, 2011 at 02:22:42PM +0800, Lin Ming wrote:
> These 4 patches add ata port runtime pm support.
> 
> v1:
> https://lkml.org/lkml/2011/11/2/23
> 
> v2 is totally different than v1.
> 
> v1 performed ata port runtime pm through scsi layer.
> Added hook to scsi host runtime suspend/resume code.
> 
> I realized that this is not the natural way to do ata port runtime pm.
> It does not deal with the races with ata port system suspend/resume.
> 
> With v2, ata port is made to be parent device of scsi host.
> 
> Currently, the device tree of ata port and scsi host looks as below,
> 
>         /sys/devices/pci0000:00/0000:00:1f.2    (ahci controller)
>         |-- ata1                                (ata port)
>         |-- host0                               (scsi host)
>            |-- target0:0:0                      (scsi target)
>                |-- 0:0:0:0                      (disk)
> 
> v2 changes it to:
> 
>         /sys/devices/pci0000:00/0000:00:1f.2    (ahci controller)
>         |-- ata1                                (ata port)
>             |-- host0                           (scsi host)
>                 |-- target0:0:0                 (scsi target)
>                     |-- 0:0:0:0                 (disk)
> 
> So ata port runtime PM will happen as:
> 
> disk suspend --> scsi target suspend --> scsi host suspend --> ata port
> suspend.
> 
> This is much cleaner and natural.

Yeah, I really like this approach.  Nicely done.  I *think* the
hierarchy change should be okay but cc'ing Kay just in case.

 Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun
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