[PATCH v7 0/4] PCI: vmd: Enable PCI PM's L1 substates of remapped PCIe Root Port and NVMe

Jian-Hong Pan
2024-06-26T09:30:07Z

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 (4):
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: Introduce aspm_get_l1ss_cap()
PCI/ASPM: Fix L1.2 parameters when enable link state

drivers/pci/controller/vmd.c | 13 ++++++++----
drivers/pci/pcie/aspm.c | 40 ++++++++++++++++++++++++++++--------
2 files changed, 40 insertions(+), 13 deletions(-)

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2.45.2