From: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> When in the ASPM L1.0 state (but not the PCI-PM L1.0 state), the most recent LTR value and the LTR_L1.2_THRESHOLD determines whether the link enters the L1.2 substate. If we don't have LTR enabled, prevent the use of ASPM L1.2. PCI-PM L1.2 may still be used because it doesn't depend on LTR_L1.2_THRESHOLD (see PCIe r4.0, sec 5.5.1). Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> --- drivers/pci/pcie/aspm.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c index f76eb7704f64..c687c817b47d 100644 --- a/drivers/pci/pcie/aspm.c +++ b/drivers/pci/pcie/aspm.c @@ -400,6 +400,15 @@ static void pcie_get_aspm_reg(struct pci_dev *pdev, info->l1ss_cap = 0; return; } + + /* + * If we don't have LTR for the entire path from the Root Complex + * to this device, we can't use ASPM L1.2 because it relies on the + * LTR_L1.2_THRESHOLD. See PCIe r4.0, secs 5.5.4, 6.18. + */ + if (!pdev->ltr_path) + info->l1ss_cap &= ~PCI_L1SS_CAP_ASPM_L1_2; + pci_read_config_dword(pdev, info->l1ss_cap_ptr + PCI_L1SS_CTL1, &info->l1ss_ctl1); pci_read_config_dword(pdev, info->l1ss_cap_ptr + PCI_L1SS_CTL2, -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
