115 lines
4.1 KiB
Verilog
115 lines
4.1 KiB
Verilog
`include "VX_platform.vh"
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module VX_rr_arbiter #(
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parameter NUM_REQS = 1,
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parameter LOCK_ENABLE = 0,
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parameter LOG_NUM_REQS = $clog2(NUM_REQS),
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parameter FAST = 1
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) (
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input wire clk,
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input wire reset,
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input wire enable,
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input wire [NUM_REQS-1:0] requests,
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output wire [LOG_NUM_REQS-1:0] grant_index,
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output wire [NUM_REQS-1:0] grant_onehot,
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output wire grant_valid
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);
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if (NUM_REQS == 1) begin
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`UNUSED_VAR (clk)
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`UNUSED_VAR (reset)
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assign grant_index = 0;
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assign grant_onehot = requests;
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assign grant_valid = requests[0];
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end else if (FAST == 1) begin
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wire [NUM_REQS-1:0] req_masked;
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wire [NUM_REQS-1:0] grant, grant_masked, grant_unmasked;
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/* verilator lint_off UNOPTFLAT */
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wire [NUM_REQS-1:0] mask_higher_pri_reqs;
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/* verilator lint_off UNOPTFLAT */
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wire [NUM_REQS-1:0] unmask_higher_pri_reqs;
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wire no_req_masked;
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reg [NUM_REQS-1:0] pointer_reg;
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// Simple priority arbitration for masked portion
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assign req_masked = requests & pointer_reg;
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assign mask_higher_pri_reqs[NUM_REQS-1:1] = mask_higher_pri_reqs[NUM_REQS-2:0] | req_masked[NUM_REQS-2:0];
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assign mask_higher_pri_reqs[0] = 1'b0;
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assign grant_masked[NUM_REQS-1:0] = req_masked[NUM_REQS-1:0] & ~mask_higher_pri_reqs[NUM_REQS-1:0];
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// Simple priority arbitration for unmasked portion
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assign unmask_higher_pri_reqs[NUM_REQS-1:1] = unmask_higher_pri_reqs[NUM_REQS-2:0] | requests[NUM_REQS-2:0];
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assign unmask_higher_pri_reqs[0] = 1'b0;
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assign grant_unmasked[NUM_REQS-1:0] = requests[NUM_REQS-1:0] & ~unmask_higher_pri_reqs[NUM_REQS-1:0];
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// Use grant_masked if there is any there, otherwise use grant_unmasked.
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assign no_req_masked = ~(| req_masked);
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assign grant = ({NUM_REQS{no_req_masked}} & grant_unmasked) | grant_masked;
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// Generate arbiter pointer update
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wire mask_ptr_sel = (| req_masked) & (!LOCK_ENABLE || enable);
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wire unmask_ptr_sel = (| requests) & (!LOCK_ENABLE || enable);
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// Pointer update
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always @(posedge clk) begin
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if (reset) begin
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pointer_reg <= {NUM_REQS{1'b1}};
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end else if (mask_ptr_sel) begin // select if masked arbiter used
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pointer_reg <= mask_higher_pri_reqs;
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end else if (unmask_ptr_sel) begin // select if unmasked arbiter used
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pointer_reg <= unmask_higher_pri_reqs;
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end
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end
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VX_onehot_encoder #(
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.N (NUM_REQS)
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) onehot_encoder (
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.data_in (grant),
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.data_out (grant_index),
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`UNUSED_PIN (valid)
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);
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assign grant_onehot = grant;
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assign grant_valid = (| requests);
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end else begin
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reg [LOG_NUM_REQS-1:0] grant_table [NUM_REQS-1:0];
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reg [LOG_NUM_REQS-1:0] state;
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always @(*) begin
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for (integer i = 0; i < NUM_REQS; i++) begin
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grant_table[i] = LOG_NUM_REQS'(i);
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for (integer j = 0; j < NUM_REQS; j++) begin
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if (requests[(i+j) % NUM_REQS]) begin
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grant_table[i] = LOG_NUM_REQS'((i+j) % NUM_REQS);
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end
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end
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end
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end
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always @(posedge clk) begin
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if (reset) begin
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state <= 0;
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end else if (!LOCK_ENABLE || enable) begin
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state <= grant_table[state];
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end
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end
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reg [NUM_REQS-1:0] grant_onehot_r;
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always @(*) begin
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grant_onehot_r = NUM_REQS'(0);
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grant_onehot_r[grant_table[state]] = 1;
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end
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assign grant_index = grant_table[state];
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assign grant_onehot = grant_onehot_r;
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assign grant_valid = (| requests);
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end
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endmodule |