Commit 9ab105de authored Apr 17, 2018 by Bjorn Helgaas

PCI/ASPM: Disable ASPM L1.2 Substate if we don't have LTR



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).

Tested-by: Srinath Mannam <srinath.mannam@broadcom.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

parent 60cc43fc

drivers/pci/pcie/aspm.c

+9 −0

Original line number	Diff line number	Diff line
		@@ -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,