[PATCH] pci: loongson: Avoid L0s on LS7A1000 PCIe x8 [0014:7a29] Root Ports rev2

[Xi Ruoyao]

Commit f3ac2ff14834 ("PCI/ASPM: Enable all ClockPM and ASPM states for
devicetree platforms") has broke booting of a Loongson 3B4000 + 7A1000
server with an Intel 750 Series SSD.  We also found a Loongson 3A5000
board using the same 7A1000 bridge chip exhibiting the same issue with
pcie_aspm=force and pcie_aspm.policy=powersave (ASPM is not enabled by
default on the 3A5000 board because it's based on ACPI and the _OSC
method has not been implemented in its DSDT/SSDT yet).

This seems only affecting the 7A1000 chips shipping the revision 2 of
the PCIe x8 Root Port: on other two boards with a (persumably older)
LS7A1000 bridge chip utilizing the revision 1 of the root port, the
issue does not reproduce.

Cc: Mingcong Bai <jeffbai@xxxxxxx>
Cc: Henry Chen <chenx97@xxxxxxx>
Cc: Han Gao <gaohan@xxxxxxxxxxx>
Cc: Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx>
Fixes: f3ac2ff14834 ("PCI/ASPM: Enable all ClockPM and ASPM states for devicetree platforms")
Signed-off-by: Xi Ruoyao <xry111@xxxxxxxxxxx>
---
 drivers/pci/controller/pci-loongson.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
index a4250d7af1bf..dc7cee10643e 100644
--- a/drivers/pci/controller/pci-loongson.c
+++ b/drivers/pci/controller/pci-loongson.c
@@ -212,6 +212,19 @@ static void loongson_pci_bridge_speed_quirk(struct pci_dev *pdev)
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_LOONGSON, 0x3c19, loongson_pci_bridge_speed_quirk);
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_LOONGSON, 0x3c29, loongson_pci_bridge_speed_quirk);
 
+/*
+ * Some devices, for example Intel 750 Series SSD, experiences data loss
+ * (read timeout) on LS7A1000 PCIe x8 Root Port when ASPM L0s is enabled.
+ * This seems only affecting the revision 2.
+ */
+static void ls7a_pcie_port2_aspm_quirk(struct pci_dev *pdev)
+{
+	if (pdev->revision == 2)
+		pcie_aspm_remove_cap(pdev, PCI_EXP_LNKCAP_ASPM_L0S);
+}
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_LOONGSON, DEV_LS7A_PCIE_PORT2,
+			 ls7a_pcie_port2_aspm_quirk);
+
 static struct loongson_pci *pci_bus_to_loongson_pci(struct pci_bus *bus)
 {
 	struct pci_config_window *cfg;
-- 
2.54.0