Re: Intel GemniLake xHCI connected devices can never wake up the system from suspend

[Daniel Drake]

On Mon, Mar 19, 2018 at 6:36 AM, Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
> On Fri, Mar 16, 2018 at 10:06 AM, Mathias Nyman
> <mathias.nyman@xxxxxxxxxxxxxxx> wrote:
>> Adding Rafael directly to CC
>>
>> In short, if _S3D and _S3W are missing in DSDT then a PCI device
>> stays in D0 during suspend in Linux, but goes to D3 in Windows.
>>
>> USB wake doesn't work in Geminilake because of this.
>>
>> Should this be changed? reasoning below.
>
> It can be changed if that doesn't cause problems to happen.

I double checked that Windows 10 is going into S3 suspend and that USB
wakeup works fine on this platform - it works fine there.
Device manager for the XHCI controller clearly shows D3 being used for
S3 suspend: https://imgur.com/lF9U3V0

Current power state:
D0

Power capabilities:
00000089
PDCAP_D0_SUPPORTED
PDCAP_D3_SUPPORTED
PDCAP_WAKE_FROM_D3_SUPPORTED

Power state mappings:
S0 -> D0
S1 -> Unspecified
S2 -> Unspecified
S3 -> D3
S4 -> D3
S5 -> D3

The biggest risk of my proposed change is that we would now end up
putting a wakeup-enabled device into a too low power state where it
can no longer wake up the system. On the other hand, it solves this
issue affecting 2 different vendors, and may even result in some power
savings in general.

Perhaps we can consider the change for inclusion in Linux-4.17, giving
2-3 months of testing time.

I'll submit the patch shortly.

Thanks
Daniel