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adding input buffering to bus arbiters to reduce backpressure delay propagation

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This commit is contained in:
Blaise Tine
2020-12-05 17:31:29 -08:00
parent 13a5370254
commit d0f2a3984d
17 changed files with 480 additions and 338 deletions
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44
hw/rtl/libs/VX_fair_arbiter.v
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@@ -7,8 +7,8 @@ module VX_fair_arbiter #(
) (
input wire clk,
input wire reset,
input wire [NUM_REQS-1:0] requests,
input wire enable,
input wire [NUM_REQS-1:0] requests,
output wire [LOG_NUM_REQS-1:0] grant_index,
output wire [NUM_REQS-1:0] grant_onehot,
output wire grant_valid
@@ -24,12 +24,13 @@ module VX_fair_arbiter #(
end else begin
reg [NUM_REQS-1:0] remaining;
wire [NUM_REQS-1:0] remaining_next;
wire [NUM_REQS-1:0] requests_use;
reg use_buffer;
reg [NUM_REQS-1:0] remaining;
reg use_buffer;
always @(posedge clk) begin
wire [NUM_REQS-1:0] requests_use = use_buffer ? remaining : requests;
wire [NUM_REQS-1:0] remaining_next = requests_use & ~grant_onehot;
always @(posedge clk) begin
if (reset) begin
remaining <= 0;
use_buffer <= 0;
@@ -38,26 +39,19 @@ module VX_fair_arbiter #(
use_buffer <= (remaining_next != 0);
end
end
assign requests_use = use_buffer ? remaining : requests;
VX_priority_encoder #(
.N(NUM_REQS)
) priority_encoder (
.data_in (requests_use),
.data_out (grant_index),
.valid_out (grant_valid)
VX_fixed_arbiter #(
.NUM_REQS(NUM_REQS),
.LOCK_ENABLE(LOCK_ENABLE)
) fixed_arbiter (
.clk (clk),
.reset (reset),
.enable (enable),
.requests (requests_use),
.grant_index (grant_index),
.grant_onehot (grant_onehot),
.grant_valid (grant_valid)
);
reg [NUM_REQS-1:0] grant_onehot_r;
always @(*) begin
grant_onehot_r = NUM_REQS'(0);
grant_onehot_r[grant_index] = 1;
end
assign remaining_next = requests_use & ~grant_onehot_r;
assign grant_onehot = grant_onehot_r;
end
endmodule