[PATCH v2 0/4] PCI/ASPM: Allow quirks to avoid L0s and L1

[Bjorn Helgaas]

From: Bjorn Helgaas <bhelgaas at 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.

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(-)

-- 

v1: https://lore.kernel.org/r/20251106183643.1963801-1-helgaas@kernel.org

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)