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Date: Thu, 6 Nov 2025 17:45:51 -0600
From: Bjorn Helgaas <helgaas@kernel.org>
To: linux-pci@vger.kernel.org
Cc: Christian Zigotzky <chzigotzky@xenosoft.de>,
	Manivannan Sadhasivam <mani@kernel.org>,
	mad skateman <madskateman@gmail.com>,
	"R . T . Dickinson" <rtd2@xtra.co.nz>,
	Darren Stevens <darren@stevens-zone.net>,
	John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
	Lukas Wunner <lukas@wunner.de>,
	luigi burdo <intermediadc@hotmail.com>, Al <al@datazap.net>,
	Roland <rol7and@gmx.com>, Hongxing Zhu <hongxing.zhu@nxp.com>,
	hypexed@yahoo.com.au, linuxppc-dev@lists.ozlabs.org,
	debian-powerpc@lists.debian.org, linux-kernel@vger.kernel.org,
	Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: [PATCH 0/2] PCI/ASPM: Allow quirks to avoid L0s and L1
Message-ID: <20251106234551.GA1976429@bhelgaas>
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In-Reply-To: <20251106183643.1963801-1-helgaas@kernel.org>

On Thu, Nov 06, 2025 at 12:36:37PM -0600, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@google.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.
> 
> 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(-)

I put these on for-linus, hopefully for v6.18.  I would like to have
some review and testing before asking Linus to pull them, especially
since the first one is not completely trivial and is a change (but
shouldn't be a functional change) for all platforms.