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 [off-list ref]

Thanks.

-- 
tejun