linux-kernel - Re: [PATCH 0/2] PCI/ASPM: Allow quirks to avoid L0s and L1

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Message-ID: <ahhrvcqpwd3ilti5fzakaojzlkfqil6vscrqgpqt7hia3igszl@vykbk65y73fj>
Date: Fri, 7 Nov 2025 11:10:08 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: linux-pci@...r.kernel.org, Christian Zigotzky <chzigotzky@...osoft.de>, 
	mad skateman <madskateman@...il.com>, "R . T . Dickinson" <rtd2@...a.co.nz>, 
	Darren Stevens <darren@...vens-zone.net>, John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>, 
	Lukas Wunner <lukas@...ner.de>, luigi burdo <intermediadc@...mail.com>, Al <al@...azap.net>, 
	Roland <rol7and@....com>, Hongxing Zhu <hongxing.zhu@....com>, hypexed@...oo.com.au, 
	linuxppc-dev@...ts.ozlabs.org, debian-powerpc@...ts.debian.org, linux-kernel@...r.kernel.org, 
	Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH 0/2] PCI/ASPM: Allow quirks to avoid L0s and L1

On Thu, Nov 06, 2025 at 12:36:37PM -0600, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@...gle.com>
> 
> We enabled ASPM too aggressively in v6.18-rc1.  f3ac2ff14834 ("PCI/ASPM:
> Enable all ClockPM and ASPM states for devicetree platforms") enabled ASPM
> L0s, L1, and (if advertised) L1 PM Substates.
> 
> L1 PM Substates and Clock PM in particular are a problem because they
> depend on CLKREQ# and sometimes device-specific configuration, and none of
> this is discoverable in a generic way.
> 
> df5192d9bb0e ("PCI/ASPM: Enable only L0s and L1 for devicetree platforms")
> (v6.18-rc3) backed off and omitted Clock PM and L1 Substates.
> 
> L0s and L1 are generically discoverable, but some devices advertise them
> even though they don't work correctly.  This series is a way to avoid L0s
> and L1 in that case.
> 

Reviewed-by: Manivannan Sadhasivam <mani@...nel.org>
Tested-by: Manivannan Sadhasivam <mani@...nel.org> # T14s

- Mani

> Bjorn Helgaas (2):
>   PCI/ASPM: Cache Link Capabilities so quirks can override them
>   PCI/ASPM: Avoid L0s and L1 on Freescale Root Ports
> 
>  drivers/pci/pcie/aspm.c | 42 ++++++++++++++++++++---------------------
>  drivers/pci/probe.c     |  5 ++---
>  drivers/pci/quirks.c    | 12 ++++++++++++
>  include/linux/pci.h     |  1 +
>  4 files changed, 36 insertions(+), 24 deletions(-)
> 
> -- 
> 2.43.0
> 

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