[PATCH] PCI/ASPM: Enable only L0s and L1 for devicetree platforms

[Bjorn Helgaas]

On Thu, Oct 23, 2025 at 08:27:25PM +0200, Dragan Simic wrote:
> On Thursday, October 23, 2025 20:06 CEST, Bjorn Helgaas <helgaas at kernel.org> wrote:
> > From: Bjorn Helgaas <bhelgaas at google.com>
> > 
> > f3ac2ff14834 ("PCI/ASPM: Enable all ClockPM and ASPM states for devicetree
> > platforms") enabled Clock Power Management and L1 PM Substates, but those
> > features depend on CLKREQ# and possibly other device-specific
> > configuration.  We don't know whether CLKREQ# is supported, so we shouldn't
> > blindly enable Clock PM and L1 PM Substates.
> > 
> > Enable only ASPM L0s and L1, and only when both ends of the link advertise
> > support for them.
> > 
> > Fixes: f3ac2ff14834 ("PCI/ASPM: Enable all ClockPM and ASPM states for devicetree platforms")
> > Reported-by: Christian Zigotzky <chzigotzky at xenosoft.de>
> > Link: https://lore.kernel.org/r/db5c95a1-cf3e-46f9-8045-a1b04908051a@xenosoft.de/
> > Reported-by: FUKAUMI Naoki <naoki at radxa.com>
> > Closes: https://lore.kernel.org/r/22594781424C5C98+22cb5d61-19b1-4353-9818-3bb2b311da0b@radxa.com/
> > Reported-by: Herve Codina <herve.codina at bootlin.com>
> > Link: https://lore.kernel.org/r/20251015101304.3ec03e6b@bootlin.com/
> > Reported-by: Diederik de Haas <diederik at cknow-tech.com>
> > Link: https://lore.kernel.org/r/DDJXHRIRGTW9.GYC2ULZ5WQAL@cknow-tech.com/
> > Signed-off-by: Bjorn Helgaas <bhelgaas at google.com>
> > Tested-by: FUKAUMI Naoki <naoki at radxa.com>
> > ---
> > I intend this for v6.18-rc3.
> > 
> > I think it will fix the issues reported by Diederik and FUKAUMI Naoki (both
> > on Rockchip).  I hope it will fix Christian's report on powerpc, but don't
> > have confirmation.  I think the performance regression Herve reported is
> > related, but this patch doesn't seem to fix it.
> > 
> > FUKAUMI Naoki's successful testing report:
> > https://lore.kernel.org/r/4B275FBD7B747BE6+a3e5b367-9710-4b67-9d66-3ea34fc30866@radxa.com/
> 
> I'm more than happy with the way ASPM patches for DT platforms and
> Rockchip SoCs in particular are unfolding!  Admittedly, we've had
> a rough start with the blanket enabling of ASPM, which followed the
> theory, but the theory often differs from practice, so the combined
> state of this and associated patches from Shawn should be fine.
> 
> Thank you very much for all the effort that included quite a lot
> of back and forth, and please feel free to include
> 
> Acked-by: Dragan Simic <dsimic at manjaro.org>

Added your ack; thanks for all your help!