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Subject[PATCH 2/8] PCI: Add ACS quirk for Amazon Annapurna Labs root ports
Date
From: Ali Saidi <alisaidi@amazon.com>

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>
---
drivers/pci/quirks.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index c66c0ca446c4..11850b030637 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -4366,6 +4366,23 @@ 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)
+{
+ /*
+ * 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_RR | PCI_ACS_CR | PCI_ACS_SV | PCI_ACS_UF);
+
+ if (pci_pcie_type(dev) != PCI_EXP_TYPE_ROOT_PORT)
+ return -ENOTTY;
+
+ 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 +4576,8 @@ 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 }
};

--
2.17.1

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