> On May 23, 2019, at 2:53 AM, Lukas Wunner <lu...@wunner.de> wrote:
>
> On Wed, May 22, 2019 at 02:39:56PM -0400, Alan Stern wrote:
>> According to Kai, PME signalling doesn't work in D0 -- or at least, it
>> is _documented_ not to work in D0 -- even though it is enabled and the
>> device claims to support it.
>>
>> In any case, I don't really see any point in "runtime suspending" a
>> device while leaving it in D0. We might as well just leave it alone.
>
> There may be devices whose drivers are able to reduce power consumption
> through some device-specific means when runtime suspending, even though
> the device remains in PCI_D0. The patch would cause a power regression
> for those.
>
> In particular, pci_target_state() returns PCI_D0 if the device lacks the
> PM capability.
So an explicit device_can_wakeup() check before calling pci_target_state()
is needed to avoid the case you described.
I’ll add this in patch v2.
Kai-Heng
>
> Thanks,
>
> Lukas
