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
