svn commit: r191674 - in head/sys/dev/ata: . chipsets

[Alexander Motin]

Alexander Leidinger wrote:
> Quoting Alexander Motin <mav at FreeBSD.org> (from Wed, 29 Apr 2009
> 21:17:18 +0000 (UTC)):
> 
>> Author: mav
>> Date: Wed Apr 29 21:17:18 2009
>> New Revision: 191674
>> URL: http://svn.freebsd.org/changeset/base/191674
>>
>> Log:
>>   Add experimental support for SATA interface power management.
>>   Feature is controlled by hint.ata.X.pm_level tunable:
>>    0 - PM disabled, old behaviour, default.
>>    1 - device is allowed to initiate PM state change, host is passive.
>>    2 - host initiates PARTIAL state transition every time port is idle.
>>    3 - host initiates SLUMBER state transition every time port is idle.
> 
> Did I miss a man-page update for this? If yes, where is it, I would have
> expected it in ata(4).

There is none yet.

>>   PARTIAL state has up to 100us (50us for me) wakeup latency, but for my
>>   ICH8M saves 0.5W of power per drive. SLUMBER state has up to 10ms
>> (3.5ms
>>   for me) wakeup latency, but saves 0.8W of power.
>>
>>   Modes 2 and 3 are implemented only for AHCI driver now.
> 
> Does this mean it is for SATA devices only, or is this a feature of the
> complete controller (ICH5 in my case) and also works with PATA drives?

This feature is SATA-specific by definition. AFAIK there is no bus power
management in PATA.

-- 
Alexander Motin