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    SubjectRe: SATA powersave patches

    > >Thanks... I got it to work (on 2 the old tree, I was not able to
    > >forward-port it), but power savings were not too big (~0.1W, maybe).
    > >
    > >I'm getting huge (~1W) savings by powering down SATA controller, as in
    > >ahci_pci_device_suspend().
    > Yeah, it only turns off SATA PHY, so it doesn't result in huge saving.
    > IIRC, it was somewhere around 5 percent on my notebook w/ static
    > linksave mode (turning PHY off on empty port). But link powersaving
    > introduces virtually no recognizable delay, so it's nice to have.

    Yes, any powersavings without cost are a good idea.

    > Can you check if there is any difference between [D/H]IPS and static?
    > ICH6M on my notebook can't do DIPS/HIPS, so I couldn't compare them
    > against static.

    What is D/HIPS? I could not find anything relevant..

    > >It would be great to be able to power SATA
    > >controller down, then power it back up when it is needed... I tried
    > >following hack, but could not get it to work. Any ideas?
    > 1. One way to do it would be by dynamic power management. It would be
    > nice to have wake-up mechanism at the block layer. Idle timer can run
    > in the block layer or it can be implemented in the userland.
    > ATM, this implies that the attached devices are powered down too
    > (spindown). As spinning up takes quite some time, we can implement

    For now, powering down controller when disks are spinned down would be
    very nice first step.

    When I forced disk to be spinned down (with power/state file)
    controller actually survived power down/power up... unfortunately with
    so long delay (~30 sec) that it is not usable in practice.

    > So, I think option #1 is the way to go - implementing leveled dynamic
    > power management infrastructure and adding support in the block layer.
    > What do you think?

    Would be nice :-).

    (cesky, pictures)
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