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

[Johan Hovold]

On Thu, Oct 23, 2025 at 01:06:26PM -0500, Bjorn Helgaas 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.

Note that this will regress ASPM on Qualcomm platforms further by
disabling L1SS for devices that do not use pwrctrl (e.g. NVMe). ASPM
with pwrctrl is already broken since 6.15. [1]

Reverting also a729c1664619 ("PCI: qcom: Remove custom ASPM enablement
code") should avoid the new regression until a proper fix for the 6.15
regression is in place.

Johan


[1] https://lore.kernel.org/lkml/aH4JPBIk_GEoAezy@hovoldconsulting.com/