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Add work-in-progress version of LI-3 version of GCD CFU.
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@grayresearch
grayresearch committed Jun 4, 2020
1 parent b8eea8d commit cd211b1
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208 changes: 203 additions & 5 deletions gcd.v
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Original file line number Diff line number Diff line change
Expand Up @@ -5,8 +5,9 @@

`include "cfu.vh"

// Test bench
module GCDTB #(
// Test bench for level-2 (variable latency with request flow control) GCD
// (greatest common divisor)
module GCDLI2TB #(
parameter CFU_FUNC_ID_W = 1,
parameter CFU_REQ_RESP_ID_W = 8,
parameter CFU_REQ_DATA_W = 32,
Expand Down Expand Up @@ -78,11 +79,11 @@ module GCDTB #(
if (resp_valid) begin
// process GCD response
if (resp_id != req_id_prev)
$display("GCDTB: FAIL: resp_id != req_id");
$display("GCD2TB: FAIL: resp_id != req_id");
else if (resp_err)
$display("GCDTB: FAIL: resp_err, resp_err_id=%1d", resp_err_id);
$display("GCD2TB: FAIL: resp_err, resp_err_id=%1d", resp_err_id);
else if (resp_data != gcdfn(a_prev, b_prev))
$display("GCDTB: FAIL: resp_data=%1d != %1d", resp_data, gcdfn(a_prev, b_prev));
$display("GCD2TB: FAIL: resp_data=%1d != %1d", resp_data, gcdfn(a_prev, b_prev));
end
end

Expand Down Expand Up @@ -116,6 +117,7 @@ CFU_LI:
- cfu_req_data_w: [32]
- cfu_resp_data_w: [32]
- cfu_err_id_w: [32]
- cfu_resp_latecy: variable
*/
module GCD_CFU_LI2 #(
parameter CFU_FUNC_ID_W = 1,
Expand Down Expand Up @@ -180,3 +182,199 @@ module GCD_CFU_LI2 #(

wire _unused_ok = &{1'b0,req_func_id,1'b0};
endmodule


// Test bench for level-3 (variable latency with request and response flow control)
// GCD (greatest common divisor)
module GCDLI3TB #(
parameter CFU_FUNC_ID_W = 1,
parameter CFU_REQ_RESP_ID_W = 8,
parameter CFU_REQ_DATA_W = 32,
parameter CFU_RESP_DATA_W = 32,
parameter CFU_ERR_ID_W = 32
) (
input clk,
input rst,
input [15:0] cycle,
input [15:0] lfsr);

function integer gcdfn(input integer a, input integer b); begin
// assumes a, b > 0
while (a != b) begin
if (a > b)
a = a - b;
else
b = b - a;
end
gcdfn = a;
end endfunction

// try asserting req_valid at "random" times
wire req_valid = !rst && lfsr[0]; // pseudo-random
wire req_ready;
reg `CFU_FUNC_ID req_func_id = 0;
reg `CFU_REQ_RESP_ID req_id;
reg `CFU_REQ_DATA a;
reg `CFU_REQ_DATA b;

// last request issued
reg `CFU_REQ_RESP_ID req_id_prev;
reg `CFU_REQ_DATA a_prev;
reg `CFU_REQ_DATA b_prev;

wire resp_valid;
wire resp_ready = ^cycle; // pseudo-random
wire `CFU_REQ_RESP_ID resp_id;
wire `CFU_RESP_DATA resp_data;
wire resp_err;
wire `CFU_ERR_ID resp_err_id;

// request GCD of (1,1), (1,2), (2,2), (1,3), (2,3), (3,3), (1,4), etc.
always @(posedge clk) begin
if (rst) begin
req_id_prev <= 0;
a_prev <= 0;
b_prev <= 0;

req_id <= 1;
a <= 1;
b <= 1;
end
else if (req_valid && req_ready) begin
// issuing the current GCD request, so prepare next request
req_id_prev <= req_id;
a_prev <= a;
b_prev <= b;

req_id <= req_id + 1;
if (a < b) begin
a <= a + 1;
end
else begin
a <= 1;
b <= b + 1;
end
end

if (resp_valid && resp_ready) begin
// process GCD response
/* if (resp_id != req_id_prev)
$display("GCD3TB: FAIL: resp_id=%1d != req_id=%1d", resp_id, req_id_prev);
else */if (resp_err)
$display("GCD3TB: FAIL: resp_err, resp_err_id=%1d", resp_err_id);
else if (resp_data != gcdfn(a_prev, b_prev))
$display("GCD3TB: FAIL: resp_data=%1d != %1d", resp_data, gcdfn(a_prev, b_prev));
end
end

// Since a <= b, perform gcd(b,a) to force at least one swap of arguments
// in GCD_CFU_LI3.
GCD_CFU_LI3 #(
.CFU_FUNC_ID_W(CFU_FUNC_ID_W),
.CFU_REQ_RESP_ID_W(CFU_REQ_RESP_ID_W),
.CFU_REQ_DATA_W(CFU_REQ_DATA_W),
.CFU_RESP_DATA_W(CFU_RESP_DATA_W),
.CFU_ERR_ID_W(CFU_ERR_ID_W))
gcd(.clk, .rst,
.req_valid, .req_ready, .req_func_id, .req_id, .req_data0(b), .req_data1(a),
.resp_valid, .resp_ready(1'b1), .resp_id, .resp_data, .resp_err, .resp_err_id);

wire _unused_ok = &{1'b0,req_id_prev,resp_id,lfsr[15:1],resp_err_id,1'b0};
endmodule


// Level-3 (variable latency with request and response flow control) GCD
// (greatest common divisor)
//
// Latency=?
// Inputs=2
// Outputs=1
//
/* Metadata
CFU_LI:
- feature_level: 2
- cfu_func_id_w: [1]
- cfu_req_data_w: [32]
- cfu_resp_data_w: [32]
- cfu_err_id_w: [32]
- cfu_resp_latecy: variable
*/
module GCD_CFU_LI3 #(
parameter CFU_FUNC_ID_W = 1,
parameter CFU_REQ_RESP_ID_W = 8,
parameter CFU_REQ_DATA_W = 32,
parameter CFU_RESP_DATA_W = 32,
parameter CFU_ERR_ID_W = 32
) (
input clk,
input rst,
input req_valid,
output reg req_ready,
input `CFU_FUNC_ID req_func_id, // unused
input `CFU_REQ_RESP_ID req_id,
input `CFU_REQ_DATA req_data0,
input `CFU_REQ_DATA req_data1,
output reg resp_valid,
input resp_ready,
output reg `CFU_REQ_RESP_ID resp_id,
output reg `CFU_RESP_DATA resp_data,
output reg resp_err,
output reg `CFU_ERR_ID resp_err_id
);
// assert(CFU_REQ_WIDTH == CFU_RESP_WIDTH);

reg `CFU_REQ_DATA a;
reg `CFU_REQ_DATA b;
reg `CFU_REQ_RESP_ID req_id_prev;

always @(posedge clk) begin
if (rst) begin
req_ready <= 1;
req_id_prev <= 0;
resp_valid <= 0;
resp_id <= 0;
resp_data <= 0;
resp_err <= 0;
resp_err_id <= 0;
end
else begin
if (req_ready) begin
// idle; await valid request
if (req_valid) begin
req_ready <= 0;
req_id_prev <= req_id;
a <= req_data0;
b <= req_data1;
end
end
else begin
// gcd in progress
if (a < b) begin
// swap a and b
a <= b;
b <= a;
end
else if (b != 0) begin
a <= a - b;
end
else begin
// have result; issue response unless previous
// response has not yet been accepted
if (!resp_valid) begin
req_ready <= 1;
resp_valid <= 1;
resp_id <= req_id_prev;
resp_data <= a;
end
end
end

// response flow control: assert response until response handshake
if (resp_valid && resp_ready) begin
resp_valid <= 0;
end
end
end

wire _unused_ok = &{1'b0,req_func_id,1'b0};
endmodule
4 changes: 3 additions & 1 deletion tb.v
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Original file line number Diff line number Diff line change
Expand Up @@ -39,5 +39,7 @@ module TB #(

MulAccSIMDTB macsimdtb(.clk, .rst, .cycle, .lfsr);

GCDTB gcdtb(.clk, .rst, .cycle, .lfsr);
GCDLI2TB gcd2tb(.clk, .rst, .cycle, .lfsr);

GCDLI3TB gcd3tb(.clk, .rst, .cycle, .lfsr);
endmodule

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