// Copyright lowRISC contributors.
// Licensed under the Apache License, Version 2.0, see LICENSE for details.
// SPDX-License-Identifier: Apache-2.0
{ name: "csrng",
  clock_primary: "clk_i",
  bus_device: "tlul",
  bus_host: "none",
  param_list: [
    { name: "NHwApps",
      type: "int",
      default: "3",
      desc: "Number of CSRNG hardware applications",
      local: "true"
    }
  ],
  interrupt_list: [
    { name: "cs_cmd_req_done"
      desc: "Asserted when a command request is completed."}
    { name: "cs_fifo_err"
      desc: "Asserted when a FIFO error occurs."}
    { name: "cs_hw_inst_exc"
      desc: "Asserted when a hardware-attached CSRNG instance encounters a command exception"}
  ],
  inter_signal_list: [
    { struct:  "csrng",  // csrng_req_t, csrng_rsp_t
      type:    "req_rsp",
      name:    "csrng_cmd",
      act:     "rsp",
      width:   "3",
      package: "csrng_pkg",
    }
    { struct:  "entropy_src_hw_if"
      type:    "req_rsp",
      name:    "entropy_src_hw_if"
      act:     "req"
      width:   1
      package: "entropy_src_pkg"
    }
    { struct:  "logic"
      type:    "uni"
      name:    "efuse_sw_app_enable"
      act:     "rcv"
      width:   1
      package: ""
    }
  ],
  regwidth: "32",
  registers: [
    { name: "REGEN",
      desc: "Register write enable for all control registers",
      swaccess: "rw1c",
      hwaccess: "hro",
      fields: [
        {
            bits:   "0",
            desc: '''
                  When true, the writeable registers can be modified.
                  When false, they become read-only. Defaults true, write one to clear. Note that this needs to be
                  cleared after initial configuration at boot in order to lock in the listed register settings.
                  '''
            resval: 1 
        },
      ]
    },
    { name: "CTRL",
      desc: "Control register",
      swaccess: "rw",
      hwaccess: "hro",
      regwen: "REGEN",
      fields: [
        {
            bits: "0",
            name: "ENABLE",
            desc: '''
                  Setting this bit will enable the CSRNG module. The application interface for software
                  (register based) will be enabled only if the respective efuse input is enabled. 
                  '''
        },
        {
            bits: "1",
            name: "AES_CIPHER_DISABLE",
            desc: '''
                  Setting this bit will disable the AES cipher core module. If set, then commands will
                  bypass the AES cipher core, but still move through the logical flow of CSRNG.
                  This mode is primarily for debug purposes.
                  '''
        },
        {
            bits: "19:16",
            name: "FIFO_DEPTH_STS_SEL",
            desc: "This field will select which FIFO depth will be read out for diagnostic purposes."
        },
      ]
    },
    {
      name: "SUM_STS",
      desc: "Summary status register",
      swaccess: "ro",
      hwaccess: "hwo",
      fields: [
        { bits: "23:0",
          name: "FIFO_DEPTH_STS",
          desc: "These bits show the current status of the CRSNG FIFO depths."
        }
        { bits: "31",
          name: "DIAG",
          desc: "This this an internal generic diagnostic bit."
        }
      ]
    },
    {
      name: "CMD_REQ",
      desc: "Command request register",
      swaccess: "wo",
      hwaccess: "hro",
      hwqe: "true",
      regwen: "REGEN",
      fields: [
        { bits: "31:0",
          name: "CMD_REQ",
          desc: '''
                Writing this request with defined CSRNG commands will initiate all
                possible CSRNG actions. The application interface must wait for the
                "ack" to return before issuing new commands.
                '''
        }
      ]
    },
    {
      name: "CMD_STS",
      desc: "Command status register",
      swaccess: "rw",
      hwaccess: "hwo",
      fields: [
        { bits: "0",
          name: "CMD_RDY",
          desc: '''This bit indicates when the command interface is ready to accept commands.
                '''
        }
        { bits: "1",
          name: "CMD_ACK",
          desc: '''This bit is set when the command request has completed. This bit must
                   be cleared before a new request is made.
                '''
        }
        { bits: "4",
          name: "CMD_STS",
          desc: '''
                This one bit field is the status code returned with the application command ack.
                0b0: Request completed successfully
                0b1: Request completed with an error
                '''
        }
      ]
    },
    {
      name: "GENBITS_VLD",
      desc: "Generate bits returned valid register",
      swaccess: "ro",
      hwaccess: "hwo",
      hwext: "true",
      fields: [
        { bits: "0",
          name: "GENBITS_VLD",
          desc: "This bit is set when genbits are available on this application interface."
        }
        { bits: "1",
          name: "GENBITS_FIPS",
          desc: "This bit is set when genbits are FIPS/CC compliant."
        }
      ]
    },
    {
      name: "GENBITS",
      desc: "Generate bits returned register",
      swaccess: "ro",
      hwaccess: "hrw",
      hwext: "true",
      hwre: "true",
      fields: [
        { bits: "31:0",
          name: "GENBITS",
          desc: '''
                Reading this register will get the generated bits that were requested with
                the generate request. This register must be four times for each request
                number made. For example, a application command generate request with 
                a `creq` value of 4 requires this register to be read 16 times to get all
                of the data out of the FIFO path.
                '''
        }
      ]
    },
    {
      name: "HW_EXC_STS",
      desc: "Hardware instance exception status register",
      swaccess: "ro",
      hwaccess: "hwo",
      fields: [
        { bits: "14:0",
          name: "HW_EXC_STS",
          desc: '''
                Reading this register indicates whether one of the CSRNG HW instances has
                encountered an exception.  Each bit corresponds to a particular hardware
                instance, with bit 0 corresponding to instance HW0, bit 1 corresponding
                to instance HW1, and so forth. (To monitor the status of requests made
                to the SW instance, check the CMD_STS register).  Uninstantiating the
                effected hardware instance, usually by a reset of the attached EDN,
                resets the corresponding status bit.
                '''
        }
        { bits: "16",
          name: "CMD_ERR",
          desc: '''
                Indicates that at least one of the instances encountered an exception
                due to an illegal command sequence (for example, requesting a generate
                operation from an uninstantiated instance, or exceeding the
                allowed seed life).  In this case, one can recover by uninstantiating
                the instance, and reinstantiating it.
                '''
        }
        { bits: "17",
          name: "ENTROPY_ERR",
          desc: '''
                Indicates that at least one of the affected instances was unable to perform an
                instantiation or reseed operation due to a failure of the entropy source.
                Troubleshooting the entropy source may be required.  Once the entropy
                source has been reinitiated, the effected instances can be reinitialized
                by uninstantiating and reinstantiating them.
		'''
	}
      ]
    }
  ]
}