On Wed, Jun 5, 2019 at 4:58 PM Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> wrote: > > Intel Ice Lake has an interated Thunderbolt controller which means that integrated > the PCIe topology is extended directly from the two root ports (RP0 and > RP1). Power management is handled by ACPI power resources that are > shared between the root ports, Thunderbolt controller (NHI) and xHCI > controller. > > The topology with the power resources (marked with []) looks like: > > Host bridge > | > +- RP0 ---\ > +- RP1 ---|--+--> [TBT] > +- NHI --/ | > | | > | v > +- xHCI --> [D3C] > > Here TBT and D3C are the shared ACPI power resources. ACPI _PR3() method > returns either TBT or D3C or both. > > Say we runtime suspend first the root ports RP0 and RP1, then NHI. Now > since the TBT power resource is still on when the root ports are runtime > suspended their dev->current_state is set to D3hot. When NHI is runtime > suspended TBT is finally turned off but state of the root ports remain > to be D3hot. It looks like this problem will affect all ACPI devices using power resources and _PR3 in general, so fixing it just for PCI is not sufficient IMO. An alternative approach may be to set the state of a device that dropped its references to power resources listed in _PR3 to D3cold even though those power resources may be physically "on" at that time. Everything else (including this patch AFAICS) will be racy this way or another.
