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 [0604]: Intel Corporation 11th Gen Core Processor PCIe Controller [8086:9a09] (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=0us LTR1.2_Threshold=0ns
L1SubCtl2: T_PwrOn=0us
10000:e1:00.0 Non-Volatile memory controller [0108]: Sandisk Corp WD Blue SN550 NVMe SSD [15b7:5009] (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=101376ns
L1SubCtl2: T_PwrOn=50us
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: ASPM: Make pci_save_aspm_l1ss_state save both child and parent's
L1SS configuration
drivers/pci/controller/vmd.c | 13 +++++++----
drivers/pci/pcie/aspm.c | 45 +++++++++++++++++++++++++++++-------
2 files changed, 46 insertions(+), 12 deletions(-)
--
2.46.2
