Re: [PATCH v8 2/2] PCI/ACPI: Use device constraints instead of dates to opt devices into D3

[Mario Limonciello]

On 8/3/23 06:38, Mario Limonciello wrote:
> On 8/3/23 00:01, Mika Westerberg wrote:
> > Hi,
> >
> > On Wed, Aug 02, 2023 at 03:10:13PM -0500, Mario Limonciello wrote:
> > > @@ -3036,11 +3044,8 @@ bool pci_bridge_d3_possible(struct pci_dev 
> > > *bridge)
> > >           if (dmi_check_system(bridge_d3_blacklist))
> > >               return false;
> > > -        /*
> > > -         * It should be safe to put PCIe ports from 2015 or newer
> > > -         * to D3.
> > > -         */
> > > -        if (dmi_get_bios_year() >= 2015)
> > > +        /* the platform indicates in a device constraint that D3 is 
> > > needed */
> > > +        if (platform_constraint_d3(bridge))
> >
> > This for sure causes some sort of power regression on the Intel
> > platforms made after 2015. Why not check for the constraint and:
> Are you sure?  I saw it as an explanation of how Windows could put the 
> systems into D3 when there is no other PM related ACPI objects.
>
> > - If present and enabled, use the desired D-state
> > - If present and disabled, leave the device in D0
> > - If not present use the existing cutoff date
> >
> > ?
>
> Thanks! That sounds very reasonable to me.  I'll double check it in my 
> case.

I've played with this a bit, and I found that I can make it work by 
moving the constraints check into pci_target_state() in the non-ACPI 
power manageable case.

To me this works pretty well to reflect spec policy ambiguity but should 
avoid regressions dropping the 2015 check.  I'll send out a v9 with this 
approach.