PCI: Add ACS quirk for iProc PAXB

iProc PAXB 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.

[bhelgaas: commit log, comment, use common implementation style]
Link: https://lore.kernel.org/r/1566275985-25670-1-git-send-email-srinath.mannam@broadcom.com
Signed-off-by: Abhinav Ratna <abhinav.ratna@broadcom.com>
Signed-off-by: Srinath Mannam <srinath.mannam@broadcom.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Scott Branden <scott.branden@broadcom.com>

drivers/pci/quirks.c

@@ -4466,6 +4466,19 @@ static int pci_quirk_mf_endpoint_acs(struct pci_dev *dev, u16 acs_flags)
 	return acs_flags ? 0 : 1;
 }
 
+static int pci_quirk_brcm_acs(struct pci_dev *dev, u16 acs_flags)
+{
+	/*
+	 * iProc PAXB 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.
+	 */
+	acs_flags &= ~(PCI_ACS_SV | PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_UF);
+
+	return acs_flags ? 0 : 1;
+}
+
 static const struct pci_dev_acs_enabled {
 	u16 vendor;
 	u16 device;
@@ -4559,6 +4572,7 @@ static const struct pci_dev_acs_enabled {
 	{ PCI_VENDOR_ID_AMPERE, 0xE00A, pci_quirk_xgene_acs },
 	{ PCI_VENDOR_ID_AMPERE, 0xE00B, pci_quirk_xgene_acs },
 	{ PCI_VENDOR_ID_AMPERE, 0xE00C, pci_quirk_xgene_acs },
+	{ PCI_VENDOR_ID_BROADCOM, 0xD714, pci_quirk_brcm_acs },
 	{ 0 }
 };