Notice the VMD remapped PCIe Root Port and NVMe have PCI PM L1 substates capability, but they are disabled originally. Here is a failed example on ASUS B1400CEAE with enabled VMD: 10000:e0:06.0 PCI bridge: Intel Corporation 11th Gen Core Processor PCIe Controller (rev 01) (prog-if 00 [Normal decode]) ... Capabilities: [200 v1] L1 PM Substates L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1+ ASPM_L1.2+ ASPM_L1.1+ L1_PM_Substates+ PortCommonModeRestoreTime=45us PortTPowerOnTime=50us L1SubCtl1: PCI-PM_L1.2- PCI-PM_L1.1- ASPM_L1.2+ ASPM_L1.1- T_CommonMode=45us LTR1.2_Threshold=101376ns L1SubCtl2: T_PwrOn=50us 10000:e1:00.0 Non-Volatile memory controller: Sandisk Corp WD Blue SN550 NVMe SSD (rev 01) (prog-if 02 [NVM Express]) ... Capabilities: [900 v1] L1 PM Substates L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1- ASPM_L1.2+ ASPM_L1.1- L1_PM_Substates+ PortCommonModeRestoreTime=32us PortTPowerOnTime=10us L1SubCtl1: PCI-PM_L1.2- PCI-PM_L1.1- ASPM_L1.2+ ASPM_L1.1- T_CommonMode=0us LTR1.2_Threshold=0ns L1SubCtl2: T_PwrOn=10us According to "PCIe r6.0, sec 5.5.4", to config the link between the PCIe Root Port and the child device correctly: * Ensure both devices are in D0 before enabling PCI-PM L1 PM Substates. * Ensure L1.2 parameters: Common_Mode_Restore_Times, T_POWER_ON and LTR_L1.2_THRESHOLD are programmed properly on both devices before enable bits for L1.2. Prepare this series to fix that. Jian-Hong Pan (3): PCI: vmd: Set PCI devices to D0 before enable PCI PM's L1 substates PCI/ASPM: Add notes about enabling PCI-PM L1SS to pci_enable_link_state(_locked) PCI: vmd: Drop resetting PCI bus action after scan mapped PCI child bus drivers/pci/controller/vmd.c | 33 +++++++++------------------------ drivers/pci/pcie/aspm.c | 6 ++++++ 2 files changed, 15 insertions(+), 24 deletions(-) -- 2.45.2