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eth: Move link speed detection logic from MAC wrapper to PHY interface

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Signed-off-by: Alex Forencich <alex@alexforencich.com>
This commit is contained in:
Alex Forencich
2025-11-13 21:27:03 -08:00
parent a919552914
commit 729bf79427
4 changed files with 142 additions and 152 deletions
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74
src/eth/rtl/taxi_gmii_phy_if.sv
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@@ -56,11 +56,73 @@ module taxi_gmii_phy_if #
output wire logic phy_gmii_tx_er,
/*
* Control
* Status
*/
input wire logic mii_select
output wire logic [1:0] link_speed
);
// PHY speed detection
logic [2:0] rx_prescale = 3'd0;
always_ff @(posedge mac_gmii_rx_clk) begin
rx_prescale <= rx_prescale + 3'd1;
end
wire rx_prescale_sync;
taxi_sync_signal #(
.WIDTH(1),
.N(2)
)
rx_prescale_sync_inst (
.clk(gtx_clk),
.in(rx_prescale[2]),
.out(rx_prescale_sync)
);
logic [6:0] rx_speed_count_1 = '0;
logic [1:0] rx_speed_count_2 = '0;
logic rx_prescale_sync_last_reg = 1'b0;
logic [1:0] link_speed_reg = '0;
assign link_speed = link_speed_reg;
always_ff @(posedge gtx_clk) begin
rx_prescale_sync_last_reg <= rx_prescale_sync;
rx_speed_count_1 <= rx_speed_count_1 + 1;
if (rx_prescale_sync ^ rx_prescale_sync_last_reg) begin
rx_speed_count_2 <= rx_speed_count_2 + 1;
end
if (&rx_speed_count_1) begin
// reference count overflow - 10M
rx_speed_count_1 <= '0;
rx_speed_count_2 <= '0;
link_speed_reg <= 2'b00;
end
if (&rx_speed_count_2) begin
// prescaled count overflow - 100M or 1000M
rx_speed_count_1 <= '0;
rx_speed_count_2 <= '0;
if (rx_speed_count_1[6:5] != 0) begin
// large reference count - 100M
link_speed_reg <= 2'b01;
end else begin
// small reference count - 1000M
link_speed_reg <= 2'b10;
end
end
if (gtx_rst) begin
rx_speed_count_1 <= '0;
rx_speed_count_2 <= '0;
link_speed_reg <= 2'b10;
end
end
taxi_ssio_sdr_in #(
.SIM(SIM),
.VENDOR(VENDOR),
@@ -92,16 +154,16 @@ if (!SIM && VENDOR == "XILINX") begin
BUFGMUX
gmii_bufgmux_inst (
.I0(gtx_clk),
.I1(phy_mii_tx_clk),
.S(mii_select),
.I0(phy_mii_tx_clk),
.I1(gtx_clk),
.S(link_speed_reg[1]),
.O(mac_gmii_tx_clk)
);
end else begin
// generic/simulation implementation (no vendor primitives)
assign mac_gmii_tx_clk = mii_select ? phy_mii_tx_clk : gtx_clk;
assign mac_gmii_tx_clk = link_speed_reg[1] ? gtx_clk : phy_mii_tx_clk;
end