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| -rw-r--r-- | Documentation/driver-api/cxl/platform/acpi/srat.rst | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/Documentation/driver-api/cxl/platform/acpi/srat.rst b/Documentation/driver-api/cxl/platform/acpi/srat.rst index 56d7bbb18c3b..cc98ca0e508e 100644 --- a/Documentation/driver-api/cxl/platform/acpi/srat.rst +++ b/Documentation/driver-api/cxl/platform/acpi/srat.rst @@ -42,3 +42,30 @@ Example :: Enabled : 1 Hot Pluggable : 1 Non-Volatile : 0 + + +Generic Port Affinity +===================== +The Generic Port Affinity subtable provides an association between a proximity +domain and a device handle representing a Generic Port such as a CXL host +bridge. With the association, latency and bandwidth numbers can be retrieved +from the SRAT for the path between CPU(s) (initiator) and the Generic Port. +This is used to construct performance coordinates for hotplugged CXL DEVICES, +which cannot be enumerated at boot by platform firmware. + +Example :: + + Subtable Type : 06 [Generic Port Affinity] + Length : 20 <- 32d, length of table + Reserved : 00 + Device Handle Type : 00 <- 0 - ACPI, 1 - PCI + Proximity Domain : 00000001 + Device Handle : ACPI0016:01 + Flags : 00000001 <- Bit 0 (Enabled) + Reserved : 00000000 + +The Proximity Domain is matched up to the :doc:`HMAT <hmat>` SSLBI Target +Proximity Domain List for the related latency or bandwidth numbers. Those +performance numbers are tied to a CXL host bridge via the Device Handle. +The driver uses the association to retrieve the Generic Port performance +numbers for the whole CXL path access coordinates calculation. |