linux-kernel - [PATCH 10/11] PCI: mvebu: Update comment for PCI_EXP

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Date:   Tue, 21 Dec 2021 15:14:54 +0100
From:   Pali Rohár <pali@...nel.org>
To:     "Thomas Petazzoni" <thomas.petazzoni@...tlin.com>,
        "Lorenzo Pieralisi" <lorenzo.pieralisi@....com>,
        "Rob Herring" <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        "Bjorn Helgaas" <bhelgaas@...gle.com>,
        Marek Behún <kabel@...nel.org>
Cc:     linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 10/11] PCI: mvebu: Update comment for PCI_EXP_LNKCTL register on emulated bridge

Logic and code for clearing PCI_EXP_LNKCTL_CLKREQ_EN bit is correct, but
comment describing it is misleading. PCI_EXP_LNKCTL_CLKREQ_EN bit should be
hardwired to zero but mvebu hw allows to change it.

Signed-off-by: Pali Rohár <pali@...nel.org>
---
 drivers/pci/controller/pci-mvebu.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/controller/pci-mvebu.c b/drivers/pci/controller/pci-mvebu.c
index 1aac65977b97..dffa330de174 100644
--- a/drivers/pci/controller/pci-mvebu.c
+++ b/drivers/pci/controller/pci-mvebu.c
@@ -663,10 +663,9 @@ mvebu_pci_bridge_emul_pcie_conf_write(struct pci_bridge_emul *bridge,
 
 	case PCI_EXP_LNKCTL:
 		/*
-		 * If we don't support CLKREQ, we must ensure that the
-		 * CLKREQ enable bit always reads zero.  Since we haven't
-		 * had this capability, and it's dependent on board wiring,
-		 * disable it for the time being.
+		 * PCIe requires that the Enable Clock Power Management bit
+		 * is hard-wired to zero for downstream ports but HW allows
+		 * to change it.
 		 */
 		new &= ~PCI_EXP_LNKCTL_CLKREQ_EN;
 
-- 
2.20.1