Messages in this thread Patch in this message |  | | From | "Carlos Bilbao (Lambda)" <> | | Subject | [PATCH] PCI/ASPM: Don't reconfigure ASPM entering low-power state | | Date | Mon, 27 Apr 2026 21:01:04 -0700 |
| |
From: Carlos Bilbao <carlos.bilbao@kernel.org>
Reconfiguring ASPM when a device transitions to low-power state can enable L1.1/L1.2 substates on the PCIe link at a time when the device is sleeping and may be unable to exit them. ASPM should be reconfigured on D0 entry (resume), not on the way down.
pci_set_low_power_state() calls pcie_aspm_pm_state_change() after writing D3hot to PCI_PM_CTRL. pcie_aspm_pm_state_change() resets link->aspm_capable to link->aspm_support and then calls pcie_config_aspm_path(), which can enable ASPM L1.1/L1.2 substates on the PCIe link. If the device cannot recover the link from L1.2 while in D3hot, subsequent config space reads return 0xFFFF ("device inaccessible") and pci_power_up() fails with message "Unable to change power state from D3hot to D0, device inaccessible".
This was observed on NVIDIA H100 SXM5 GPUs bound to vfio-pci when Linux runtime PM suspends them to D3hot: the GPU becomes permanently inaccessible and disappears from the PCIe bus.
The call to pcie_aspm_pm_state_change() in pci_set_low_power_state() was restored by commit f93e71aea6c6 ("Revert "PCI/ASPM: Remove pcie_aspm_pm_state_change()""), which reverted commit 08d0cc5f3426 ("PCI/ASPM: Remove pcie_aspm_pm_state_change()"). The revert was necessary because the removal broke suspend/resume on certain platforms that required ASPM to be reconfigured on D0 entry. However, the revert restored the call in both pci_set_full_power_state() (D0 entry) and pci_set_low_power_state() (low-power entry).
Only the D0-entry call is needed to fix the suspend/resume regression. The low-power-entry call is harmful: reconfiguring ASPM immediately after putting a device into D3hot can enable link substates that the device or platform cannot exit while the device is sleeping.
Remove the pcie_aspm_pm_state_change() call from pci_set_low_power_state(). ASPM will still be reconfigured correctly when the device returns to D0 via pci_set_full_power_state().
Fixes: f93e71aea6c6 ("Revert "PCI/ASPM: Remove pcie_aspm_pm_state_change()"") Link: https://lore.kernel.org/r/20240102232550.1751655-1-helgaas@kernel.org Signed-off-by: Carlos Bilbao (Lambda) <carlos.bilbao@kernel.org> --- drivers/pci/pci.c | 3 --- 1 file changed, 3 deletions(-)
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index b2ccb8e122f2..8b47887019f9 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -1542,9 +1542,6 @@ static int pci_set_low_power_state(struct pci_dev *dev, pci_power_t state, bool pci_power_name(dev->current_state), pci_power_name(state)); - if (dev->bus->self) - pcie_aspm_pm_state_change(dev->bus->self, locked); - return 0; } -- 2.50.1 (Apple Git-155)
|  |