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>
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@ -400,6 +400,15 @@ static void pcie_get_aspm_reg(struct pci_dev *pdev,
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info->l1ss_cap = 0;
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return;
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}
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/*
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* If we don't have LTR for the entire path from the Root Complex
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* to this device, we can't use ASPM L1.2 because it relies on the
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* LTR_L1.2_THRESHOLD. See PCIe r4.0, secs 5.5.4, 6.18.
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*/
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if (!pdev->ltr_path)
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info->l1ss_cap &= ~PCI_L1SS_CAP_ASPM_L1_2;
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pci_read_config_dword(pdev, info->l1ss_cap_ptr + PCI_L1SS_CTL1,
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&info->l1ss_ctl1);
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pci_read_config_dword(pdev, info->l1ss_cap_ptr + PCI_L1SS_CTL2,
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