Commit 1ce91b37 authored by Dave Jiang's avatar Dave Jiang
Browse files

cxl: docs/platform/acpi/srat Add generic target documentation 



Add description in the SRAT document to describe the Generic Port
Affinity sub-table.

Reviewed-by: default avatarGregory Price <gourry@gourry.net>
Reviewed-by: default avatarAlison Schofield <alison.schofield@intel.com>
Link: https://patch.msgid.link/20250515000923.2590820-3-dave.jiang@intel.com


Signed-off-by: default avatarDave Jiang <dave.jiang@intel.com>
parent 49cee8fe

Documentation/driver-api/cxl/platform/acpi/srat.rst

+27 −0
Original line number Diff line number Diff line
@@ -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.