ErrorMagnitude.bsv

//----------------------------------------------------------------------//
// The MIT License
//
// Copyright (c) 2008 Abhinav Agarwal, Alfred Man Cheuk Ng
// Contact: abhiag@gmail.com
//
// Permission is hereby granted, free of charge, to any person
// obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without
// restriction, including without limitation the rights to use,
// copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.
//----------------------------------------------------------------------//

import FIFO::*;
import Vector::*;
import GFTypes::*;
import RSParameters::*;
import GFArith::*;

// ---------------------------------------------------------
// Reed-Solomon Error Magnitude computer interface
// ---------------------------------------------------------
interface IErrorMagnitude;
    method Action              k_in(Byte k_new);
    method Action              no_error_flag_in(Bool no_error_new);
    method Action              loc_in(Maybe#(Byte) loc_new);
    method Action              alpha_inv_in(Maybe#(Byte) alpha_inv_new);
    method Action              lambda_in(Syndrome#(T) lambda_new);
    method Action              omega_in(Syndrome#(T) omega_new);

    method ActionValue#(Byte)  error_out();
endinterface

// ---------------------------------------------------------
// Reed-Solomon Error Magnitude computer module
// ---------------------------------------------------------
(* synthesize *)
module mkErrorMagnitude (IErrorMagnitude);

    // input queues
    FIFO#(Byte)             k_q             <- mkSizedFIFO(1);
    FIFO#(Bool)             no_error_flag_q <- mkSizedFIFO(1);
    FIFO#(Syndrome#(T))     lambda_q        <- mkSizedFIFO(1);
    FIFO#(Syndrome#(T))     omega_q         <- mkSizedFIFO(1);
    FIFO#(Maybe#(Byte))     loc_q           <- mkSizedFIFO(valueOf(TwoT));
    FIFO#(Maybe#(Byte))     alpha_inv_q     <- mkSizedFIFO(valueOf(T));

    // output queues
    FIFO#(Byte)             err_q           <- mkSizedFIFO(2);

    // internal quques
    FIFO#(Byte)             int_err_q       <- mkSizedFIFO(valueOf(T));

    // booking state
    Reg#(Byte)              omega_val       <- mkReg(0);
    Reg#(Byte)              lambda_d_val    <- mkReg(0);

    Reg#(Byte)              i               <- mkReg(0);
    Reg#(Byte)              count           <- mkReg(0);
    Reg#(Byte)              block_number    <- mkReg(1);

    // variables
    Byte t = fromInteger(valueOf(T));
    let k = k_q.first();
    let no_error_flag = no_error_flag_q.first();
    let loc = fromMaybe(255,loc_q.first()); // next location has no error?
    let alpha_inv = fromMaybe(?,alpha_inv_q.first());
    let lambda = lambda_q.first();
    let omega  = omega_q.first();

    // -----------------------------------------------
    rule eval_lambda_omega (count < t && isValid(alpha_inv_q.first()));
        // Derivative of Lambda is done by dropping even terms and shifting odd terms by one
        // So count is incremented by 2
        // valid_t - 2 is the index used as the final term since valid_t - 1 term gets dropped
        Byte idx = (t - 1) - count;
        Byte lambda_add_val = ((count & 8'd1) == 8'd1) ? lambda[idx] : 0;
        lambda_d_val <= gf_add(gf_mult(lambda_d_val, alpha_inv),lambda_add_val);
        omega_val <= gf_mult(omega_val, alpha_inv) ^ omega[idx];
        count <= count + 1;

        $display ("  [errMag %d]  Evaluating Lambda_der count : %d, lambda_d_val[prev] : %d, lambda_add_val : %d, idx : %d",
                block_number, count, lambda_d_val, lambda_add_val, idx);
        $display ("  [errMag %d]  Evaluating Omega count : %d, omega_val[prev] : %d",
                block_number, count, omega_val);
    endrule

    // ------------------------------------------------
    rule enq_error (count == t);
        $display ("  [errMag %d]  Finish Evaluating Lambda Omega", block_number);
        let err_val = gf_mult(omega_val, gf_inv(lambda_d_val));
        int_err_q.enq(err_val);
        count <= 0;
        lambda_d_val <= 0;
        omega_val <= 0;
        alpha_inv_q.deq();
    endrule

    rule deq_invalid_alpha_inv (alpha_inv_q.first() matches Invalid);
        $display ("  [errMag %d]  Deq Invalid Alpha Inv", block_number);
        alpha_inv_q.deq();
        lambda_q.deq();
        omega_q.deq();
    endrule

    // ------------------------------------------------
    rule process_error_no_error (i < k && !no_error_flag);
        Byte err_val;
        if (i == loc) begin
            $display ("  [errMag %d]  Processing location %d which is in error ", block_number, i);
            err_val = int_err_q.first();
            int_err_q.deq();
            loc_q.deq();
        end else begin
            $display ("  [errMag %d]  process location %d which has no error ", block_number, i);
            err_val = 0;
        end
        err_q.enq(err_val);
        i <= i + 1;
    endrule

    // ------------------------------------------------
    rule bypass(i < k && no_error_flag);
        $display ("  [errMag %d]  process location %d bypass which has no error ", block_number, i);
        i <= k;
    endrule

    // ------------------------------------------------
    rule start_next_errMag (i == k);
        $display ("Start Next ErrMag");
        k_q.deq();
        no_error_flag_q.deq();
        i <= 0;
        block_number <= block_number + 1;
        if (!no_error_flag)
            loc_q.deq(); // this one should be the Invalid denomiator
    endrule

    // ------------------------------------------------
    method Action k_in(Byte k_new);
        $display ("  [errMag %d]  k_in : %d", block_number, k_new);
        k_q.enq(k_new);
    endmethod

    // ------------------------------------------------
    method Action no_error_flag_in(Bool no_error_new);
        $display ("  [errMag %d]  no_error_flag_in : %d", block_number, no_error_new);
        no_error_flag_q.enq(no_error_new);
    endmethod

    // ------------------------------------------------
    method Action loc_in(Maybe#(Byte) loc_new);
        $display ("  [errMag %d]  loc_in : %d", block_number, loc_new);
        loc_q.enq(loc_new);
    endmethod

    // ------------------------------------------------
    method Action alpha_inv_in(Maybe#(Byte) alpha_inv_new);
        $display ("  [errMag %d]  alpha_inv_in : %d", block_number, alpha_inv_new);
        alpha_inv_q.enq(alpha_inv_new);
    endmethod

    // ------------------------------------------------
    method Action lambda_in(Syndrome#(T) lambda_new);
        $display ("  [errMag %d]  lambda_in : %d", block_number, lambda_new);
        lambda_q.enq(lambda_new);
    endmethod

    // ------------------------------------------------
    method Action omega_in(Syndrome#(T) omega_new);
        $display ("  [errMag %d]  w_in : %d", block_number, omega_new);
        omega_q.enq(omega_new);
    endmethod

    // ------------------------------------------------
    method ActionValue#(Byte) error_out();
        $display ("  [errMag %d]  err_out: %d", block_number, err_q.first());
        err_q.deq();
        return err_q.first();
    endmethod
endmodule