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    SubjectRe: [RFC PATCH] PCIe: Add PCIe runtime D3cold support
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    On Wed, Apr 18, 2012 at 4:20 AM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
    > On Tuesday, April 17, 2012, huang ying wrote:
    >> On Tue, Apr 17, 2012 at 1:07 AM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
    >> > Moreover, I really don't think it's a good idea to put PCI Express ports into
    >> > low-power states in general.  It might work on your platform, whatever it is,
    >> > but that doesn't mean it's going to work on every PCI Express system out
    >> > there.  I actually know of a number of such systems where it surely won't
    >> > work at all.
    >>
    >> The runtime PM support for PCIe port is not turned on by default, we need
    >>
    >> # echo auto > /sys/devices/pcixxxx:xx/<pci id>/power/control
    >>
    >> to turn on it.  And we will turn on it on system it works.  Is this sufficient?
    >
    > No, it is not.  In some cases it shouldn't be enabled at all for PCI Express
    > ports, as far as I can say, so to be on the safe side we should only enable it
    > on platforms where PCI Express ports are known to work correctly with runtime PM.

    Sorry, I did not catch your idea exactly. I think disable it by
    default and enable it by sysfs interface is what you suggested, isn't
    it? Or you suggest something like "white list"?

    Best Regards,
    Huang Ying
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