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PCI: dwc: Advertise L1 PM Substates only if driver requests it

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[ Upstream commit a00bba406b ]

L1 PM Substates require the CLKREQ# signal and may also require
device-specific support.  If CLKREQ# is not supported or driver support is
lacking, enabling L1.1 or L1.2 may cause errors when accessing devices,
e.g.,

  nvme nvme0: controller is down; will reset: CSTS=0xffffffff, PCI_STATUS=0x10

If the kernel is built with CONFIG_PCIEASPM_POWER_SUPERSAVE=y or users
enable L1.x via sysfs, users may trip over these errors even if L1
Substates haven't been enabled by firmware or the driver.

To prevent such errors, disable advertising the L1 PM Substates unless the
driver sets "dw_pcie.l1ss_support" to indicate that it knows CLKREQ# is
present and any device-specific configuration has been done.

Set "dw_pcie.l1ss_support" in tegra194 (if DT includes the
"supports-clkreq' property) and qcom (for cfg_2_7_0, cfg_1_9_0, cfg_1_34_0,
and cfg_sc8280xp controllers) so they can continue to use L1 Substates.

Based on Niklas's patch:
https://patch.msgid.link/20251017163252.598812-2-cassel@kernel.org

[bhelgaas: drop hiding for endpoints]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/20251118214312.2598220-2-helgaas@kernel.org
Stable-dep-of: 180c3cfe36 ("Revert "PCI: dw-rockchip: Enumerate endpoints based on dll_link_up IRQ"")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Bjorn Helgaas 2025-11-18 15:42:15 -06:00 • committed by Sasha Levin
commit b1f114b7a6
5 changed files with 33 additions and 0 deletions
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