PCI: Add ACS quirk for Amazon Annapurna Labs root ports

The Amazon's Annapurna Labs root ports don't advertise an ACS
capability, but they don't allow peer-to-peer transactions and do
validate bus numbers through the SMMU. Additionally, it's not possible
for one RP to pass traffic to another RP.

Signed-off-by: Ali Saidi <alisaidi@amazon.com>
Signed-off-by: Jonathan Chocron <jonnyc@amazon.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Reviewed-by: Andrew Murray <andrew.murray@arm.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 208aacf39329..e96c03b4e494 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -4366,6 +4366,24 @@ static int pci_quirk_qcom_rp_acs(struct pci_dev *dev, u16 acs_flags)
         return ret;
 }
 
+static int pci_quirk_al_acs(struct pci_dev *dev, u16 acs_flags)
+{
+        if (pci_pcie_type(dev) != PCI_EXP_TYPE_ROOT_PORT)
+                return -ENOTTY;
+
+        /*
+         * Amazon's Annapurna Labs root ports don't include an ACS capability,
+         * but do include ACS-like functionality. The hardware doesn't support
+         * peer-to-peer transactions via the root port and each has a unique
+         * segment number.
+         *
+         * Additionally, the root ports cannot send traffic to each other.
+         */
+        acs_flags &= ~(PCI_ACS_SV | PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_UF);
+
+        return acs_flags ? 0 : 1;
+}
+
 /*
  * Sunrise Point PCH root ports implement ACS, but unfortunately as shown in
  * the datasheet (Intel 100 Series Chipset Family PCH Datasheet, Vol. 2,
@@ -4559,6 +4577,8 @@ 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 },
+        /* Amazon Annapurna Labs */
+        { PCI_VENDOR_ID_AMAZON_ANNAPURNA_LABS, 0x0031, pci_quirk_al_acs },
         { 0 }
 };