linux-kernel - Re: [PATCH] PCI/ASPM: Enable only L0s and L1 for devicetree platforms

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Message-ID: <aPuZQRaTN2tAwkb5@hovoldconsulting.com>
Date: Fri, 24 Oct 2025 17:20:33 +0200
From: Johan Hovold <johan@...nel.org>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: linux-pci@...r.kernel.org,
	Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>,
	Christian Zigotzky <chzigotzky@...osoft.de>,
	FUKAUMI Naoki <naoki@...xa.com>,
	Herve Codina <herve.codina@...tlin.com>,
	Diederik de Haas <diederik@...ow-tech.com>,
	Dragan Simic <dsimic@...jaro.org>, linuxppc-dev@...ts.ozlabs.org,
	linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH] PCI/ASPM: Enable only L0s and L1 for devicetree platforms

On Fri, Oct 24, 2025 at 05:12:38PM +0200, Johan Hovold wrote:
> On Thu, Oct 23, 2025 at 01:06:26PM -0500, Bjorn Helgaas wrote:
> > From: Bjorn Helgaas <bhelgaas@...gle.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@...osoft.de>
> > Link: https://lore.kernel.org/r/db5c95a1-cf3e-46f9-8045-a1b04908051a@xenosoft.de/
> > Reported-by: FUKAUMI Naoki <naoki@...xa.com>
> > Closes: https://lore.kernel.org/r/22594781424C5C98+22cb5d61-19b1-4353-9818-3bb2b311da0b@radxa.com/
> > Reported-by: Herve Codina <herve.codina@...tlin.com>
> > Link: https://lore.kernel.org/r/20251015101304.3ec03e6b@bootlin.com/
> > Reported-by: Diederik de Haas <diederik@...ow-tech.com>
> > Link: https://lore.kernel.org/r/DDJXHRIRGTW9.GYC2ULZ5WQAL@cknow-tech.com/
> > Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
> > Tested-by: FUKAUMI Naoki <naoki@...xa.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]

Actually, the 6.15 regression was fixed in 6.18-rc1 by the offending
commit, but pwrctrl devices will now also regress again.

> 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/