PCI: Add ACS quirk for Loongson PCIe

BugLink: https://bugs.launchpad.net/bugs/2120812

commit 1f3303aa92e15fa273779acac2d0023609de30f1 upstream.

Loongson PCIe Root Ports don't advertise an ACS capability, but they do not
allow peer-to-peer transactions between Root Ports. Add an ACS quirk so
each Root Port can be in a separate IOMMU group.

Signed-off-by: Xianglai Li <lixianglai@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20250403040756.720409-1-chenhuacai@loongson.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Noah Wager <noah.wager@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

Author: chenhuacai

drivers/pci/quirks.c

@@ -5010,6 +5010,18 @@ static int pci_quirk_brcm_acs(struct pci_dev *dev, u16 acs_flags)
 		PCI_ACS_SV | PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_UF);
 }
 
+static int pci_quirk_loongson_acs(struct pci_dev *dev, u16 acs_flags)
+{
+	/*
+	 * Loongson PCIe Root Ports don't advertise an ACS capability, but
+	 * they do not allow peer-to-peer transactions between Root Ports.
+	 * Allow each Root Port to be in a separate IOMMU group by masking
+	 * SV/RR/CR/UF bits.
+	 */
+	return pci_acs_ctrl_enabled(acs_flags,
+		PCI_ACS_SV | PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_UF);
+}
+
 /*
  * Wangxun 40G/25G/10G/1G NICs have no ACS capability, but on
  * multi-function devices, the hardware isolates the functions by
@@ -5143,6 +5155,17 @@ static const struct pci_dev_acs_enabled {
 	{ PCI_VENDOR_ID_BROADCOM, 0x1762, pci_quirk_mf_endpoint_acs },
 	{ PCI_VENDOR_ID_BROADCOM, 0x1763, pci_quirk_mf_endpoint_acs },
 	{ PCI_VENDOR_ID_BROADCOM, 0xD714, pci_quirk_brcm_acs },
+	/* Loongson PCIe Root Ports */
+	{ PCI_VENDOR_ID_LOONGSON, 0x3C09, pci_quirk_loongson_acs },
+	{ PCI_VENDOR_ID_LOONGSON, 0x3C19, pci_quirk_loongson_acs },
+	{ PCI_VENDOR_ID_LOONGSON, 0x3C29, pci_quirk_loongson_acs },
+	{ PCI_VENDOR_ID_LOONGSON, 0x7A09, pci_quirk_loongson_acs },
+	{ PCI_VENDOR_ID_LOONGSON, 0x7A19, pci_quirk_loongson_acs },
+	{ PCI_VENDOR_ID_LOONGSON, 0x7A29, pci_quirk_loongson_acs },
+	{ PCI_VENDOR_ID_LOONGSON, 0x7A39, pci_quirk_loongson_acs },
+	{ PCI_VENDOR_ID_LOONGSON, 0x7A49, pci_quirk_loongson_acs },
+	{ PCI_VENDOR_ID_LOONGSON, 0x7A59, pci_quirk_loongson_acs },
+	{ PCI_VENDOR_ID_LOONGSON, 0x7A69, pci_quirk_loongson_acs },
 	/* Amazon Annapurna Labs */
 	{ PCI_VENDOR_ID_AMAZON_ANNAPURNA_LABS, 0x0031, pci_quirk_al_acs },
 	/* Zhaoxin multi-function devices */