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

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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>
This commit is contained in:
Bjorn Helgaas 2018-04-17 11:25:51 -05:00
parent 60cc43fc88
commit 9ab105deb6
1 changed files with 9 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

9
drivers/pci/pcie/aspm.c
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@ -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,