RE: [PATCH v13 01/12] PCI: Only put Intel PCIe ports >= 2015 into D3

[David Laight <David.Laight@ACULAB.COM>]

From: Rafael J. Wysocki
> Sent: Friday, August 18, 2023 9:12 AM
> 
> On Fri, Aug 18, 2023 at 7:14 AM Mario Limonciello
> <mario.limonciello@amd.com> wrote:
> >
> > commit 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during suspend")
> > changed pci_bridge_d3_possible() so that any vendor's PCIe ports
> > from modern machines (>=2015) are allowed to be put into D3.
> >
> > Iain reports that USB devices can't be used to wake a Lenovo Z13
> > from suspend. This is because the PCIe root port has been put
> > into D3 and AMD's platform can't handle USB devices waking in this
> > case.
> >
...
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index 60230da957e0c..051e88ee64c63 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -3037,10 +3037,11 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge)
> >                         return false;
> >
> >                 /*
> > -                * It should be safe to put PCIe ports from 2015 or newer
> > +                * It is safe to put Intel PCIe ports from 2015 or newer
> >                  * to D3.
> >                  */
> 
> I would say "Allow Intel PCIe ports from 2015 onward to go into D3 to
> achieve additional energy conservation on some platforms" without the
> "It is safe" part that is kind of obvious (it wouldn't be done if it
> were unsafe).

Just say why...

"Don't put root ports into D3 on non-Intel systems to avoid issues
with USB devices being unable to wake up some AMD based laptops."

	David

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