On Fri, Jul 08, 2016 at 11:25:03AM +0300, Mika Westerberg wrote:
> On Fri, Jul 08, 2016 at 01:54:48AM +0200, Peter Wu wrote:
> > Allow the nouveau driver to find out whether the bridge can put itself
> > in the D3cold state or whether it should use a specific DSM method to
> > achieve the same result.
> >
> > Cc: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> > Signed-off-by: Peter Wu <peter@xxxxxxxxxxxxx>
> > ---
> > Since it is not yet merged in Linus tree, maybe the patch in pci/pm can be
> > amended? This is the follow-up patch I had in mind for nouveau:
> >
> > --- a/drivers/gpu/drm/nouveau/nouveau_acpi.c
> > +++ b/drivers/gpu/drm/nouveau/nouveau_acpi.c
> > @@ -223,6 +223,9 @@ static bool nouveau_pr3_present(struct pci_dev *pdev)
> > if (!parent_pdev)
> > return false;
> >
> > + if (!pci_bridge_d3_possible(parent_pdev))
> > + return false;
> > +
>
> Why not check bridge_d3 directly?
>
> if (!parent_dev->bridge_d3)
> return false;
I have thought of that but then dismissed the idea because
pci_bridge_d3_update could change it after initialization based on the
d3cold_allowed flag on the bridge or its children. Then this could
happen:
- initially d3cold_allowed is set false by the user
- nouveau decides to use DSM
- d3cold_allowed is set by user to true
- PCI thinks that power resources are OK to use, but that conflicts
with nouveau.
Hmm, maybe it is usable, but then something like this is needed:
/* Initially assume that D3cold is OK. */
pci_d3cold_enable(pdev);
if (!parent_dev->bridge_d3) {
/* bridge does not support D3cold, keep it disabled. */
pci_d3cold_disable(pdev);
return false;
}
How does that look?
--
Kind regards,
Peter Wu
https://lekensteyn.nl
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