From: Sinan Kaya <okaya@codeaurora.org>
Date: Mon, 22 Jan 2018 15:12:01 -0500
Subject: PCI/ASPM: Don't warn if already in common clock mode
Git-commit: 04875177dbe034055f23960981ecf6fb8ea1d638
Patch-mainline: 4.17-rc1
References: git-fixes

Previously we emitted a warning if we tried to configure common clock mode
the link was already configured to common clock mode by the UEFI BIOS.
Bail out silently in that case instead of emitting the warning:

  pci 0004:00:00.0: ASPM: Could not configure common clock

Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
[bhelgaas: changelog]
Signed-off-by: Bjorn Helgaas <helgaas@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/pci/pcie/aspm.c |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -227,6 +227,24 @@ static void pcie_aspm_configure_common_c
 	if (!(reg16 & PCI_EXP_LNKSTA_SLC))
 		same_clock = 0;
 
+	/* Port might be already in common clock mode */
+	pcie_capability_read_word(parent, PCI_EXP_LNKCTL, &reg16);
+	if (same_clock && (reg16 & PCI_EXP_LNKCTL_CCC)) {
+		bool consistent = true;
+
+		list_for_each_entry(child, &linkbus->devices, bus_list) {
+			pcie_capability_read_word(child, PCI_EXP_LNKCTL,
+						  &reg16);
+			if (!(reg16 & PCI_EXP_LNKCTL_CCC)) {
+				consistent = false;
+				break;
+			}
+		}
+		if (consistent)
+			return;
+		pci_warn(parent, "ASPM: current common clock configuration is broken, reconfiguring\n");
+	}
+
 	/* Configure downstream component, all functions */
 	list_for_each_entry(child, &linkbus->devices, bus_list) {
 		pcie_capability_read_word(child, PCI_EXP_LNKCTL, &reg16);