The 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:
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
Power on all of the VMD remapped PCI devices before enable PCI-PM L1 PM
Substates by following PCI Express Base Specification Revision 6.0, section
5.5.4.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=218394
Signed-off-by: Jian-Hong Pan <[email protected]>
---
drivers/pci/controller/vmd.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
index 87b7856f375a..6aca3f77724c 100644
--- a/drivers/pci/controller/vmd.c
+++ b/drivers/pci/controller/vmd.c
@@ -751,11 +751,9 @@ static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
if (!(features & VMD_FEAT_BIOS_PM_QUIRK))
return 0;
- pci_enable_link_state_locked(pdev, PCIE_LINK_STATE_ALL);
-
pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_LTR);
if (!pos)
- return 0;
+ goto out_enable_link_state;
/*
* Skip if the max snoop LTR is non-zero, indicating BIOS has set it
@@ -763,7 +761,7 @@ static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
*/
pci_read_config_dword(pdev, pos + PCI_LTR_MAX_SNOOP_LAT, <r_reg);
if (!!(ltr_reg & (PCI_LTR_VALUE_MASK | PCI_LTR_SCALE_MASK)))
- return 0;
+ goto out_enable_link_state;
/*
* Set the default values to the maximum required by the platform to
@@ -775,6 +773,13 @@ static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
pci_write_config_dword(pdev, pos + PCI_LTR_MAX_SNOOP_LAT, ltr_reg);
pci_info(pdev, "VMD: Default LTR value set by driver\n");
+out_enable_link_state:
+ /*
+ * Ensure devices are in D0 before enabling PCI-PM L1 PM Substates, per
+ * PCIe r6.0, sec 5.5.4.
+ */
+ pci_set_power_state_locked(pdev, PCI_D0);
+ pci_enable_link_state_locked(pdev, PCIE_LINK_STATE_ALL);
return 0;
}
--
2.43.0