Re: [PATCH] PCI/ASPM: Don't reconfigure ASPM entering low-power state

[Bjorn Helgaas]

On Mon, Apr 27, 2026 at 09:01:04PM -0700, Carlos Bilbao (Lambda) wrote:
> From: Carlos Bilbao <carlos.bilbao@xxxxxxxxxx>
> 
> 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".

Carlos, do you have a few lines of dmesg showing this issue that we
could quote to help people match the issue with this fix?