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    SubjectRe: Time to re-enable Runtime PM per default for PCI devcies?
    On Thu, Dec 31, 2020 at 10:38:12AM +0100, Heiner Kallweit wrote:
    > On 31.12.2020 05:07, Lukas Wunner wrote:
    > > FWIW, if platform_pci_power_manageable() returns true, it can probably
    > > be assumed that allowing runtime PM by default is okay. So as a first
    > > step, you may want to call that instead of adding a new callback.
    >
    > I don't think that's sufficient. Most likely all the broken old systems
    > return true for platform_pci_power_manageable().

    platform_pci_power_manageable() is not a global flag, but rather
    a per-device flag whether the platform is capable of power-managing
    that device. E.g. for the ACPI platform, it indicates that objects
    such as _PS0 or _PS3 are present in the device's namespace.

    My point is that if the platform can power-manage a device,
    then it ought to be safe to enable runtime PM by default for it.

    If you insist on a "big hammer" approach by turning on runtime PM
    by default for everything, you risk regressions. You can avoid
    that by going for a smart approach which enables runtime PM in
    cases when it's safe.

    Thanks,

    Lukas

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