Re: [PATCH v2] PCI: PM: Skip devices in D0 for suspend-to-idle

From: Rafael J. Wysocki
Date: Mon Jun 24 2019 - 17:37:45 EST

On Mon, Jun 24, 2019 at 2:43 PM Jon Hunter <jonathanh@xxxxxxxxxx> wrote:
> Hi Rafael,
> On 13/06/2019 22:59, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> >
> > Commit d491f2b75237 ("PCI: PM: Avoid possible suspend-to-idle issue")
> > attempted to avoid a problem with devices whose drivers want them to
> > stay in D0 over suspend-to-idle and resume, but it did not go as far
> > as it should with that.
> >
> > Namely, first of all, the power state of a PCI bridge with a
> > downstream device in D0 must be D0 (based on the PCI PM spec r1.2,
> > sec 6, table 6-1, if the bridge is not in D0, there can be no PCI
> > transactions on its secondary bus), but that is not actively enforced
> > during system-wide PM transitions, so use the skip_bus_pm flag
> > introduced by commit d491f2b75237 for that.
> >
> > Second, the configuration of devices left in D0 (whatever the reason)
> > during suspend-to-idle need not be changed and attempting to put them
> > into D0 again by force is pointless, so explicitly avoid doing that.
> >
> > Fixes: d491f2b75237 ("PCI: PM: Avoid possible suspend-to-idle issue")
> > Reported-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> > Tested-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
> I have noticed a regression in both the mainline and -next branches on
> one of our boards when testing suspend. The bisect is point to this
> commit and reverting on top of mainline does fix the problem. So far I
> have not looked at this in close detail but kernel log is showing ...

Can you please collect a log like that, but with dynamic debug in
pci-driver.c enabled?

Note that reverting this commit is rather out of the question, so we
need to get to the bottom of the failure.