svn commit: r191674 - in head/sys/dev/ata: . chipsets
mav at FreeBSD.org
Wed Jun 17 13:10:32 UTC 2009
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
>> 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
>> 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.
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