On Tue, Jun 25, 2019 at 12:00:57PM +0200, Rafael J. Wysocki wrote: > On Tue, Jun 25, 2019 at 11:46 AM Mika Westerberg > <mika.westerberg@xxxxxxxxxxxxxxx> wrote: > > > > On Mon, Jun 24, 2019 at 01:14:47PM +0200, Rafael J. Wysocki wrote: > > > > The problem here is that acpi_device_get_power() really only should be > > > > used for two purposes: (1) To initialize adev->power.state, or to > > > > update it via acpi_device_update_power(), and (2) by the > > > > "real_power_state" sysfs attribute (of ACPI device objects). The > > > > adev->power.state value should be used anywhere else, in principle, so > > > > the Mika's patch is correct. > > > > > > Well, it is an improvement, but it is not sufficient. > > > > > > > [Note that adev->power.state cannot be updated after calling > > > > acpi_device_get_power() to the value returned by it without updating > > > > the reference counters of the power resources that are "on" *exactly* > > > > because of the problem at hand here.] > > > > > > That is obviously correct, but -> > > > > > > > > but that's just an idle thought, not a suggestion. > > > > > > > > After the initialization of the ACPI subsystem, the authoritative > > > > source of the ACPI device power state information is > > > > adev->power.state. The ACPI subsystem is expected to update this > > > > value as needed going forward (including system-wide transitions like > > > > resume from S3). > > > > > > -> the "resume from S3 or hibernation" case needs special handling, because > > > in that case the device power state need not reflect the information the ACPI > > > subsystem has. That only matters if adev->power.state is ACPI_STATE_D0 and > > > the device is actually *not* in D0, because in that case acpi_device_set_power() > > > will not work. > > > > I guess you are talking about the special-cased devices that we leave in > > D0 when system suspend (via firmware) is entered? > > > > > So that case is not covered currently (it should be rare in practice, > > > though, if it happens at all), so something like the patch below (untested) may > > > be needed in addition to the Mika's patch. > > > > Looks good to me. > > I actually decided to address this issue in acpi_device_set_power() as > it may affect devices beyond PCI in principle. I will send a patch > for that shortly. Thanks! > > > Still, there is also the "power state not matching" case in pci_pm_complete() that's > > > need to be covered and the non-PCI ACPI PM has a similar issue in theory, so I > > > need to think about this a bit more. > > > > Do you want me to hold off sending an updated version of the patch > > series while we figure this one out or is it fine if I send it out now > > and we can add further details on top? > > It is independent of the other fix, so it can be sent now just fine IMO. OK, I'll send it out in a minute.
