linux-kernel - [PATCH V2] PCI/ASPM: Suppress common clock mode setting failure

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Date:   Mon, 22 Jan 2018 15:12:01 -0500
From:   Sinan Kaya <okaya@...eaurora.org>
To:     linux-pci@...r.kernel.org, timur@...eaurora.org
Cc:     linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Sinan Kaya <okaya@...eaurora.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rajat Jain <rajatja@...gle.com>,
        Vidya Sagar <vidyas@...dia.com>,
        Yinghai Lu <yinghai@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Kees Cook <keescook@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH V2] PCI/ASPM: Suppress common clock mode setting failure

Code is emitting warnings when it tries to set the common clock mode for
ASPM and ASPM is already configured to common clock mode by the UEFI BIOS.
Let's bail out silently in such a case.

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

Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
---
 drivers/pci/pcie/aspm.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 9783e10..913b90d 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -240,6 +240,24 @@ static void pcie_aspm_configure_common_clock(struct pcie_link_state *link)
 	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;
+		dev_warn(&parent->dev, "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);
-- 
1.9.1