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5. OpenAMP RemoteProc (Under Discussion)

Note

The contents of this chapter are still under discussion.

[OpenAMP] RemoteProc is a framework for remote processor lifecycle management and inter-processor communication between Linux and other operating systems.

[Lopper] can translate System Device Tree domain descriptions into the Linux remoteproc representation used by AMD Xilinx platforms.

5.1. Overview

The current Xilinx remoteproc binding is xlnx,zynqmp-r5fss.yaml. It covers three subsystem compatibles:

xlnx,zynqmp-r5fss
xlnx,versal-r5fss
xlnx,versal-net-r52fss

The generated Linux node is a remoteproc subsystem node with one or more processor children:

the subsystem node carries compatible, #address-cells, #size-cells, ranges, xlnx,cluster-mode, and, for ZynqMP and Versal R5F, xlnx,tcm-mode
each processor child carries compatible, reg, reg-names, power-domains, and optionally memory-region, mboxes, mbox-names, and sram

In the current domain YAML flow, Linux remoteproc generation is driven by a domain-to-domain relation compatible with openamp,remoteproc-v2. A matching openamp,rpmsg-v1 relation can then extend the same processor child with RPMsg carveouts and mailbox properties.

5.2. System Device Tree Representation

The System Device Tree input does not need a dedicated remoteproc node. Instead, the required information is distributed across:

top-level reserved-memory nodes for DDR carveouts
the remote domain cpus entry for the target RPU core
the remote domain sram list for TCM, local SRAM, or DDR boot staging regions used during image loading
domain-to-domain relations for remoteproc-v2 and rpmsg-v1

The current shipped domain YAML overlays in meta-xilinx-standalone-sdt/conf/domainyaml follow this model.

5.2.1. System Device Tree Example

The following YAML matches the current ZynqMP overlay style and contains enough information for lopper to generate a Linux remoteproc node conforming to the current binding.

reserved-memory:
  ranges: true
  "#size-cells": 2
  "#address-cells": 2

  rproc0@9800000:
    start: 0x9800000
    size: 0x60000
    no-map: 1

  vdev0vring0@9860000:
    start: 0x9860000
    size: 0x4000
    no-map: 1

  vdev0vring1@9864000:
    start: 0x9864000
    size: 0x4000
    no-map: 1

  vdev0buffer@9868000:
    start: 0x9868000
    size: 0x100000
    no-map: 1

domains:
  APU_Linux:
    compatible: openamp,domain-v1
    cpus:
      - cluster: cpus_a53
        cpumask: 0xf
        mode:
          secure: true
          el: 0x3
    os,type: linux
    reserved-memory:
      - vdev0buffer@9868000
      - vdev0vring1@9864000
      - vdev0vring0@9860000
      - rproc0@9800000

    domain-to-domain:
      compatible: openamp,domain-to-domain-v1

      remoteproc-relation:
        compatible: openamp,remoteproc-v2
        relation0:
          remote: R5_0_FREERTOS
          elfload:
            - psu_r5_0_atcm_global@ffe00000
            - psu_r5_0_btcm_global@ffe20000
            - rproc0@9800000

      rpmsg-relation:
        compatible: openamp,rpmsg-v1
        relation0:
          remote: R5_0_FREERTOS
          mbox: ipi_7_to_ipi_1
          carveouts:
            - vdev0vring0@9860000
            - vdev0vring1@9864000
            - vdev0buffer@9868000
          timer: [ ttc0, ttc1 ]

  R5_0_FREERTOS:
    compatible: openamp,domain-v1
    cpus:
      - cluster: cpus_r5_0
        cluster_cpu: psu_cortexr5_0
        cpumask: 0x1
        mode:
          secure: true
          el: 0x3
    os,type: freertos
    sram:
      - dev: rproc0@9800000
        start: 0x9800000
        size: 0x60000
      - dev: psu_r5_0_atcm_global@ffe00000
        start: 0xffe00000
        size: 64K
      - dev: psu_r5_0_btcm_global@ffe20000
        start: 0xffe20000
        size: 64K
    reserved-memory:
      - vdev0buffer@9868000
      - vdev0vring1@9864000
      - vdev0vring0@9860000
      - rproc0@9800000

5.2.2. Conversion Rules

Lopper derives the Linux remoteproc node as follows:

The platform selects the subsystem compatible: xlnx,zynqmp-r5fss, xlnx,versal-r5fss, or xlnx,versal-net-r52fss.
The remote domain cpus entry selects the target processor child and the xlnx,cluster-mode value.
On ZynqMP and Versal R5F, xlnx,tcm-mode is emitted and follows the same split or lockstep setting as xlnx,cluster-mode.
elfload entries that refer to TCM memories become the processor child’s reg and reg-names entries.
elfload entries that refer to DDR carveouts become the first memory-region entries.
carveouts from the matching openamp,rpmsg-v1 relation are appended to memory-region in Linux order: firmware image, vdev0buffer, vring0, vring1.
The RPMsg mailbox endpoint becomes mboxes and mbox-names = "tx", "rx" on the processor child.
power-domains are derived from the target core and the referenced TCM memories.

The binding-specific memory layout differs by platform:

ZynqMP and Versal R5F use ATCM and BTCM banks. In split mode each child typically exposes atcm0 and btcm0. In lockstep mode the binding expects the combined ATCM and BTCM banks and xlnx,tcm-mode = <1>.
Versal Net and Versal2 R52F use ATCM, BTCM, and CTCM banks. These platforms do not use xlnx,tcm-mode in the binding.

5.2.3. Generated Linux Device Tree Example

The following Linux DTS fragment is representative of the output that lopper generates for the previous YAML example. Provider nodes are omitted for brevity.

reserved-memory {
    #address-cells = <2>;
    #size-cells = <2>;
    ranges;

    rproc0_reserved: rproc0@9800000 {
        no-map;
        reg = <0x0 0x09800000 0x0 0x00060000>;
    };

    vdev0vring0: vdev0vring0@9860000 {
        no-map;
        reg = <0x0 0x09860000 0x0 0x00004000>;
    };

    vdev0vring1: vdev0vring1@9864000 {
        no-map;
        reg = <0x0 0x09864000 0x0 0x00004000>;
    };

    vdev0buffer: vdev0buffer@9868000 {
        compatible = "shared-dma-pool";
        no-map;
        reg = <0x0 0x09868000 0x0 0x00100000>;
    };
};

remoteproc@ffe00000 {
    compatible = "xlnx,zynqmp-r5fss";
    #address-cells = <2>;
    #size-cells = <2>;
    ranges = <0x0 0x0 0x0 0xffe00000 0x0 0x10000>,
             <0x0 0x20000 0x0 0xffe20000 0x0 0x10000>;
    xlnx,cluster-mode = <0>;
    xlnx,tcm-mode = <0>;

    r5f@0 {
        compatible = "xlnx,zynqmp-r5f";
        reg = <0x0 0x0 0x0 0x10000>,
              <0x0 0x20000 0x0 0x10000>;
        reg-names = "atcm0", "btcm0";
        power-domains = <&zynqmp_firmware 0x7>,
                        <&zynqmp_firmware 0xf>,
                        <&zynqmp_firmware 0x10>;
        memory-region = <&rproc0_reserved>,
                        <&vdev0buffer>,
                        <&vdev0vring0>,
                        <&vdev0vring1>;
        mboxes = <&ipi_mailbox_rpu0 0>, <&ipi_mailbox_rpu0 1>;
        mbox-names = "tx", "rx";
    };
};

5.2.4. Notes

The old xlnx,zynqmp-r5-remoteproc and xilinx,r5f examples are stale and should not be used as the reference form.
memory-region is for DDR reserved-memory carveouts. TCM banks are described by the processor child’s reg and reg-names entries.
The optional sram property in the binding remains available for additional on-chip SRAM regions outside the core-local TCM layout.