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    SubjectRe: [patch 0/3] AHCI Link Power Management
    Arjan van de Ven wrote:
    > Tejun Heo wrote:
    >> Kristen Carlson Accardi wrote:
    >>> Hi,
    >>> This series of patches enables Aggressive Link Power Management for
    >>> AHCI devices, as documented in the AHCI spec. On my laptop (a Lenovo
    >>> X60), this
    >>> saves me a full watt of power. On other systems, reported power savings
    >>> range from .5-1.5 Watts. It has been tested by the kind folks at
    >>> #powertop
    >>> with similar results. Please give it a try and let me know what you
    >>> think.
    >>
    >> I'm not sure about this. We need better PM framework to support
    >> powersaving in other controllers and some ahcis don't save much when
    >> only link power management is used,
    >
    > do you have data to support this? The data we have from this patch is
    > that it saves typically a Watt of power (depends on the machine of
    > course, but the range is 0.5W to 1.5W). If you want to also have an even
    > more agressive thing where you want to start disabling the entire
    > controller... I don't see how this is in conflict with saving power on
    > the link level by "just" enabling a hardware feature ....

    SATA standard defines lower power phy states. So the same argument
    you're using for AHCI applies there too -- "just" enabling an existing
    hardware feature.

    Jeff


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