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Multiple Devices per Host Bridge

Documentation/driver-api/cxl/platform/example-configurations/multi-dev-per-hb.rst

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.. SPDX-License-Identifier: GPL-2.0

================================ Multiple Devices per Host Bridge

In this example system we will have a single socket and one CXL host bridge. There are two CXL memory expanders with 4GB attached to the host bridge.

Things to note:

  • Intra-Bridge interleave is not described here.
  • The expanders are described by a single CEDT/CFMWS.
  • This CEDT/SRAT describes one node for both devices.
  • There is only one proximity domain the HMAT for both devices.

:doc:CEDT <../acpi/cedt>::

        Subtable Type : 00 [CXL Host Bridge Structure]
             Reserved : 00
               Length : 0020

Associated host bridge : 00000007 Specification version : 00000001 Reserved : 00000000 Register base : 0000010370400000 Register length : 0000000000010000

        Subtable Type : 01 [CXL Fixed Memory Window Structure]
             Reserved : 00
               Length : 002C
             Reserved : 00000000
  Window base address : 0000001000000000
          Window size : 0000000200000000

Interleave Members (2^n) : 00 Interleave Arithmetic : 00 Reserved : 0000 Granularity : 00000000 Restrictions : 0006 QtgId : 0001 First Target : 00000007

:doc:SRAT <../acpi/srat>::

     Subtable Type : 01 [Memory Affinity]
            Length : 28
  Proximity Domain : 00000001
         Reserved1 : 0000
      Base Address : 0000001000000000
    Address Length : 0000000200000000
         Reserved2 : 00000000

Flags (decoded below) : 0000000B Enabled : 1 Hot Pluggable : 1 Non-Volatile : 0

:doc:HMAT <../acpi/hmat>::

           Structure Type : 0001 [SLLBI]
                Data Type : 00   [Latency]

Target Proximity Domain List : 00000000 Target Proximity Domain List : 00000001 Entry : 0080 Entry : 0100

           Structure Type : 0001 [SLLBI]
                Data Type : 03   [Bandwidth]

Target Proximity Domain List : 00000000 Target Proximity Domain List : 00000001 Entry : 1200 Entry : 0200

:doc:SLIT <../acpi/slit>::

 Signature : "SLIT"    [System Locality Information Table]
Localities : 0000000000000003

Locality 0 : 10 20 Locality 1 : FF 0A

:doc:DSDT <../acpi/dsdt>::

Scope (_SB) { Device (S0D0) { Name (_HID, "ACPI0016" /* Compute Express Link Host Bridge */) // _HID: Hardware ID ... Name (_UID, 0x07) // _UID: Unique ID } ... }