Re: PCI/ASPM: Allow quirks to avoid L0s and L1

[Roland]

Hello all!

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Regards,

Roland



> On Mon, Nov 10, 2025 at 04:22:24PM -0600, Bjorn Helgaas wrote:
>> From: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
>> 
>> 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.
>> 
>> df5192d9bb0e ("PCI/ASPM: Enable only L0s and L1 for devicetree
>> platforms") (v6.18-rc3) backed off and omitted Clock PM and L1 Substates
>> because we don't have good infrastructure to discover CLKREQ# support,
>> and L1 Substates may require device-specific configuration.
>> 
>> L0s and L1 are generically discoverable and should not require
>> device-specific support, but some devices advertise them even though
>> they don't work correctly.  This series is a way to add quirks avoid L0s
>> and L1 in this case.
>> 
>> 
>> Bjorn Helgaas (4):
>>   PCI/ASPM: Cache L0s/L1 Supported so advertised link states can be
>>     overridden
>>   PCI/ASPM: Add pcie_aspm_remove_cap() to override advertised link
>>     states
>>   PCI/ASPM: Convert quirks to override advertised link states
>>   PCI/ASPM: Avoid L0s and L1 on Freescale Root Ports
>> 
>>  drivers/pci/pci.h       |  2 ++
>>  drivers/pci/pcie/aspm.c | 25 +++++++++++++++++--------
>>  drivers/pci/probe.c     |  7 +++++++
>>  drivers/pci/quirks.c    | 38 +++++++++++++++++++-------------------
>>  include/linux/pci.h     |  2 ++
>>  5 files changed, 47 insertions(+), 27 deletions(-)
>
> Applied to pci/for-linus, hoping for v6.18.  Thanks Shawn and Lukas
> for testing and reviewing.  Any other comments and testing would be
> very welcome.
>
> I think we'll need to add a similar quirk for Christian's X1000
> (https://lore.kernel.org/r/a41d2ca1-fcd9-c416-b111-a958e92e94bf@xxxxxxxxxxx),
> but I don't know the device ID for it yet.
>
>> -- 
>> 
>> v1:
>> https://lore.kernel.org/r/20251106183643.1963801-1-helgaas@xxxxxxxxxx
>
>> Changes between v1 and v2:
>> - Cache just the two bits for L0s and L1 support, not the entire Link
>>   Capabilities (Lukas)
>> - Add pcie_aspm_remove_cap() to override the ASPM Support bits in Link
>>   Capabilities (Lukas)
>> - Convert existing quirks to use pcie_aspm_remove_cap() instead of
>>   pci_disable_link_state(), and from FINAL to HEADER (Mani)
Regards