hw/ip/otbn/data/otbn.hjson

// Copyright lowRISC contributors.
// Licensed under the Apache License, Version 2.0, see LICENSE for details.
// SPDX-License-Identifier: Apache-2.0
{ name: "otbn"
  clock_primary: "clk_i"
  bus_device: "tlul"
  bus_host: "none"
  interrupt_list: [
    { name: "done"
      desc: "OTBN has completed the operation"
    }
    { name: "err"
      desc: "An error occurred. Read the ERR_CODE register for error details."
    }
  ]
  alert_list: [
    { name: "imem_uncorrectable"
      desc: "Uncorrectable error in the instruction memory detected."
    }
    { name: "dmem_uncorrectable"
      desc: "Uncorrectable error in the data memory detected."
    }
    { name: "reg_uncorrectable"
      desc: "Uncorrectable error in one of the register files detected."
    }
  ]

  inter_signal_list: [
    // TODO: CSRNG isn't committed yet, depends on assumed interface done for
    // AES in https://github.com/lowRISC/opentitan/pull/2140.
    /*{ name:    "entropy",
      type:    "req_rsp",
      act:     "req",
      package: "csrng_pkg",
      struct:  "csrng_entropy",
      width:   "1"
    },*/

    // OTBN is not performing any operation and can be clock/power-gated.
    { name:    "idle",
      type:    "uni",
      struct:  "logic",
      width:   "1",
      act:     "req",
    },
  ],

  regwidth: "32"
  registers: [
    { name: "CMD"
      desc: "command register",
      swaccess: "r0w1c",
      hwaccess: "hro",
      hwext: "true",
      hwqe:  "true",
      fields: [
        { bits: "0"
          name: "start"
          desc: '''
            Start the operation

            The completion is signalled by the done interrupt.
          '''
          tags: [// Do not randomly start big num operations
                 "excl:CsrNonInitTests:CsrExclWrite"],
        }
        { bits: "1",
          name: "dummy",
          desc: '''
            Reggen doesn't generate sub-fields with only a single field
            specified; instead, the whole register is taken as a field, leading
            to signals like `hw2reg.status.d` instead of
            `hw2reg.status.start.d`. Since we expect to add more commands later,
            we force the generation of fields with this dummy field for now.
          '''
        }
      ],
    }
    { name: "STATUS",
      desc: "Status",
      swaccess: "ro",
      hwaccess: "hwo",
      hwext: "true",
      fields: [
        { bits: "0",
          name: "busy",
          desc: "OTBN is performing an operation."
        }
        { bits: "1",
          name: "dummy",
          desc: '''
            See !!CMD.dummy for details.
          '''
        }
      ]
    } // register : status
    { name: "ERR_CODE",
      desc: "Error Code",
      swaccess: "ro",
      hwaccess: "hwo",
      fields: [
        { bits: "31:0",
          name: "err_code",
          desc: '''
            The error cause if an error occurred.

            TODO: Define error codes.

            Software should read this register before clearing the err
            interrupt to avoid race conditions.
          '''
        }
      ]
    } // register : err_code
    { name: "START_ADDR",
      desc: "Start byte address in the instruction memory",
      swaccess: "wo",
      hwaccess: "hro",
      fields: [
        { bits: "31:0",
          name: "start_addr",
          resval: 0,
          desc: '''
            Byte address in the instruction memory OTBN starts to execute from
            when instructed to do so with the !!CMD.start .
          '''
        }
      ]
    } // register : start_addr


    // Give IMEM and DMEM 1 MB address space, each, to allow for easy expansion
    // of the actual IMEM and DMEM sizes without changing the address map.
    { skipto: "0x100000" }

    { window: {
        name: "IMEM"
        items: "1024" // 4 kB
        swaccess: "rw",
        byte-write: "false",
        desc: '''
          Instruction Memory.

          Not accessible during the operation of the engine.
          TODO: Discuss and document behavior in that case. Alert? Ignore?
        '''
      }
    }

    { skipto: "0x200000" }

    { window: {
        name: "DMEM"
        items: "1024" // 4 kB
        swaccess: "rw",
        byte-write: "false",
        desc: '''
          Data Memory.

          Not accessible during the operation of the engine.
          TODO: Discuss and document behavior in that case. Alert? Ignore?
        '''
      }
    }
  ]
}