// Copyright lowRISC contributors.
// Licensed under the Apache License, Version 2.0, see LICENSE for details.
// SPDX-License-Identifier: Apache-2.0
//
// kmac_pkg

package kmac_pkg;

  // import necessary functions from sha3_pkg
  import sha3_pkg::*;
  export sha3_pkg::MsgWidth;
  export sha3_pkg::MsgStrbW;

  // Message FIFO depth
  //
  // Assume entropy is ready always (if Share is reused as an entropy in Chi)
  // Then it takes 72 cycles to complete the Keccak round. While Keccak is in
  // operation, the module need to store the incoming messages to not degrade
  // the throughput.
  //
  // Based on the observation from HMAC case, the core usually takes 5 clocks
  // to fetch data and store into KMAC. So the core can push at most 14.5 X 4B
  // which is 58B. After that, Keccak can fetch the data from MSG_FIFO faster
  // rate than the core can push. To fetch 58B, it takes around 7~8 cycles.
  // For that time, the core only can push at most 2 DW. After that Keccak
  // waits the incoming message.
  //
  // So Message FIFO doesn't need full block size except the KMAC case, which
  // is delayed the operation by processing Function Name N, customization S,
  // and secret keys. But KMAC doesn't need high throughput anyway (72Mb/s).
  parameter int RegIntfWidth = 32; // 32bit interface
  parameter int RegLatency   = 5;  // 5 cycle to write one Word
  parameter int Sha3Latency  = 72; // Expected masked sha3 processing time 24x3

  // Total required buffer size while SHA3 is in processing
  parameter int BufferCycles   = (Sha3Latency + RegLatency - 1)/RegLatency;
  parameter int BufferSizeBits = RegIntfWidth * BufferCycles;

  // Required MsgFifoDepth. Adding slightly more buffer for margin
  parameter int MsgFifoDepth   = 2 + ((BufferSizeBits + MsgWidth - 1)/MsgWidth);
  parameter int MsgFifoDepthW  = $clog2(MsgFifoDepth+1);

  parameter int MsgWindowWidth = 32; // Register width
  parameter int MsgWindowDepth = 512; // 2kB space

  // Key related definitions
  // If this value is changed, please modify the logic inside kmac_core
  // that assigns the value into `encoded_key`
  parameter int MaxKeyLen = 512;

  // size of encode_string(Key)
  // $ceil($clog2(MaxKeyLen+1)/8)
  parameter int MaxEncodedKeyLenW = $clog2(MaxKeyLen+1);
  parameter int MaxEncodedKeyLenByte = (MaxEncodedKeyLenW + 8 - 1) / 8;
  parameter int MaxEncodedKeyLenSize = MaxEncodedKeyLenByte * 8;

  //                             Secret Key  left_encode(len(Key))
  //                             ----------  ------------------------
  parameter int MaxEncodedKeyW = MaxKeyLen + MaxEncodedKeyLenSize + 8;

  // key_len is SW configurable CSR.
  // Current KMAC allows 5 key length options.
  // This value determines the KMAC core how to map the value
  // from Secret Key register to key size block
  typedef enum logic [2:0] {
    Key128 = 3'b 000, // 128 bit secret key
    Key192 = 3'b 001, // 192 bit secret key
    Key256 = 3'b 010, // 256 bit secret key
    Key384 = 3'b 011, // 384 bit secret key
    Key512 = 3'b 100  // 512 bit secret key
  } key_len_e;


  // kmac_cmd_e defines the possible command sets that software issues via
  // !!CMD register. This is mainly to limit the error scenario that SW writes
  // multiple commands at once.
  typedef enum logic [3:0] {
    CmdNone      = 4'b 0000,
    CmdStart     = 4'b 0001,
    CmdProcess   = 4'b 0010,
    CmdManualRun = 4'b 0100,
    CmdDone      = 4'b 1000
  } kmac_cmd_e;

  ////////////////////
  // Error Handling //
  ////////////////////

  // Error structure is same to the SHA3 one. The codes do not overlap.
  typedef enum logic [7:0] {
    ErrNone = 8'h 00,

    // ErrSha3SwControl occurs when software sent wrong flow signal.
    // e.g) Sw set `process_i` without `start_i`. The state machine ignores
    //      the signal and report through the error FIFO.
    //ErrSha3SwControl = 8'h 80

    // ErrKeyNotValid: KeyMgr interface raises an error if the secret key is
    // not valid when KeyMgr initiates KDF.
    ErrKeyNotValid = 8'h 01,

    // ErrSwPushMsgFifo: Sw writes data into Msg FIFO abruptly.
    // This error occurs in below scenario:
    //   - Sw does not send "Start" command to KMAC then writes data into
    //     Msg FIFO
    //   - Sw writes data into Msg FIFO when KeyMgr is in operating
    ErrSwPushedMsgFifo = 8'h 02,

    // ErrSwPushWrongCmd
    //  - Sw writes any command except CmdStart when Idle.
    ErrSwPushedWrongCmd = 8'h 03
  } err_code_e;

  typedef struct packed {
    logic        valid;
    err_code_e   code; // Type of error
    logic [23:0] info; // Additional Debug info
  } err_t;

  ///////////////////////
  // Library Functions //
  ///////////////////////

  // Endian conversion functions (32-bit, 64-bit)
  function automatic logic [31:0] conv_endian32( input logic [31:0] v, input logic swap);
    logic [31:0] conv_data = {<<8{v}};
    conv_endian32 = (swap) ? conv_data : v ;
  endfunction : conv_endian32

  function automatic logic [63:0] conv_endian64( input logic [63:0] v, input logic swap);
    logic [63:0] conv_data = {<<8{v}};
    conv_endian64 = (swap) ? conv_data : v ;
  endfunction : conv_endian64

endpackage : kmac_pkg