Messages in this thread | | | Date | Mon, 4 Jan 2021 18:39:44 +0100 | From | Lukas Wunner <> | Subject | Re: Time to re-enable Runtime PM per default for PCI devcies? |
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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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