On Thu, Oct 19, 2017 at 01:17:31AM +0200, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > > The motivation for this change is to provide a way to work around > a problem with the direct-complete mechanism used for avoiding > system suspend/resume handling for devices in runtime suspend. > > The problem is that some middle layer code (the PCI bus type and > the ACPI PM domain in particular) returns positive values from its > system suspend ->prepare callbacks regardless of whether the driver's > ->prepare returns a positive value or 0, which effectively prevents > drivers from being able to control the direct-complete feature. > Some drivers need that control, however, and the PCI bus type has > grown its own flag to deal with this issue, but since it is not > limited to PCI, it is better to address it by adding driver flags at > the core level. > > To that end, add a driver_flags field to struct dev_pm_info for flags > that can be set by device drivers at the probe time to inform the PM > core and/or bus types, PM domains and so on on the capabilities and/or > preferences of device drivers. Also add two static inline helpers > for setting that field and testing it against a given set of flags > and make the driver core clear it automatically on driver remove > and probe failures. > > Define and document two PM driver flags related to the direct- > complete feature: NEVER_SKIP and SMART_PREPARE that can be used, > respectively, to indicate to the PM core that the direct-complete > mechanism should never be used for the device and to inform the > middle layer code (bus types, PM domains etc) that it can only > request the PM core to use the direct-complete mechanism for > the device (by returning a positive value from its ->prepare > callback) if it also has been requested by the driver. > > While at it, make the core check pm_runtime_suspended() when > setting power.direct_complete so that it doesn't need to be > checked by ->prepare callbacks. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
