linux-kernel - [PATCH v5] PCI: loongson: Use DECLARE_PCI_FIXUP_EARLY for bridge_class

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Message-Id: <1595065176-460-1-git-send-email-yangtiezhu@loongson.cn>
Date:   Sat, 18 Jul 2020 17:39:36 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Huacai Chen <chenhc@...ote.com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>
Cc:     linux-mips@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, Xuefeng Li <lixuefeng@...ngson.cn>
Subject: [PATCH v5] PCI: loongson: Use DECLARE_PCI_FIXUP_EARLY for bridge_class_quirk()

According to the datasheet of Loongson LS7A bridge chip, the old version
of Loongson LS7A PCIE port has a wrong value about PCI class which is
0x060000, the correct value should be 0x060400, this bug can be fixed by
"dev->class = PCI_CLASS_BRIDGE_PCI << 8;" at the software level. As far
as I know, the latest version of LS7A has already fixed the value at the
hardware level.

In order to maintain downward compatibility, use DECLARE_PCI_FIXUP_EARLY
instead of DECLARE_PCI_FIXUP_HEADER for bridge_class_quirk() to fix it as
early as possible.

Otherwise, in the function pci_setup_device(), the related code about
"dev->class" such as "class = dev->class >> 8;" and "dev->transparent
= ((dev->class & 0xff) == 1);" maybe get wrong value without EARLY fixup.

Fixes: 1f58cca5cf2b ("PCI: Add Loongson PCI Controller support")
Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
---

v2: Modify the patch subject used with lower case "loongson"

v3: Update the commit message

v4: Update the commit message to describe the bug

v5: Remove "due to" in the commit message suggested by Sergei Shtylyov

 drivers/pci/controller/pci-loongson.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
index 459009c..58b862a 100644
--- a/drivers/pci/controller/pci-loongson.c
+++ b/drivers/pci/controller/pci-loongson.c
@@ -37,11 +37,11 @@ static void bridge_class_quirk(struct pci_dev *dev)
 {
 	dev->class = PCI_CLASS_BRIDGE_PCI << 8;
 }
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_LOONGSON,
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
 			DEV_PCIE_PORT_0, bridge_class_quirk);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_LOONGSON,
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
 			DEV_PCIE_PORT_1, bridge_class_quirk);
-DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_LOONGSON,
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
 			DEV_PCIE_PORT_2, bridge_class_quirk);
 
 static void system_bus_quirk(struct pci_dev *pdev)
-- 
2.1.0