[PATCH V4] pci: quirk: Apply APM ACS quirk to XGene devices

[Feng Kan]

The APM X-Gene PCIe root port does not support ACS at this point.
However, the hw provides isolation and source validation through
the SMMU. The stream ID generated by the PCIe ports contain both
the BDF as well as the port ID in its 3 most significant bits.
Turn on ACS but disable all the peer to peer features.

Signed-off-by: Feng Kan <fkan@xxxxxxx>
---
	V4 Change: Remove TB & TD flags from ACS mask
        V3 Change: Add comment regarding unique port id in stream ID
        V2 Change: Move XGene ACS quirk to unique XGene function

 drivers/pci/quirks.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 085fb78..22343b3 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -4120,6 +4120,18 @@ static int pci_quirk_cavium_acs(struct pci_dev *dev, u16 acs_flags)
 	return acs_flags ? 0 : 1;
 }
 
+static int pci_quirk_xgene_acs(struct pci_dev *dev, u16 acs_flags)
+{
+	/*
+	 * XGene root matching this quirk do not allow peer-to-peer
+	 * transactions with others, allowing masking out these bits as if they
+	 * were unimplemented in the ACS capability.
+	 */
+	acs_flags &= ~(PCI_ACS_SV | PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_UF);
+
+	return acs_flags ? 0 : 1;
+}
+
 /*
  * Many Intel PCH root ports do provide ACS-like features to disable peer
  * transactions and validate bus numbers in requests, but do not provide an
@@ -4368,6 +4380,8 @@ static int pci_quirk_mf_endpoint_acs(struct pci_dev *dev, u16 acs_flags)
 	{ 0x10df, 0x720, pci_quirk_mf_endpoint_acs }, /* Emulex Skyhawk-R */
 	/* Cavium ThunderX */
 	{ PCI_VENDOR_ID_CAVIUM, PCI_ANY_ID, pci_quirk_cavium_acs },
+	/* APM XGene */
+	{ PCI_VENDOR_ID_AMCC, 0xE004, pci_quirk_xgene_acs },
 	{ 0 }
 };
 
-- 
1.8.3.1