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eth: Optimize frame length enforcement logic in BASE-R MACs

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Signed-off-by: Alex Forencich <alex@alexforencich.com>
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Alex Forencich
2025-10-03 15:49:51 -07:00
parent 8257fdf09e
commit 04df834708
8 changed files with 224 additions and 76 deletions
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38
src/eth/rtl/taxi_axis_xgmii_rx_32.sv
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@@ -130,7 +130,9 @@ logic is_mcast_reg = 1'b0, is_mcast_next;
logic is_bcast_reg = 1'b0, is_bcast_next;
logic is_8021q_reg = 1'b0, is_8021q_next;
logic [15:0] frame_len_reg = '0, frame_len_next;
logic [15:0] frame_len_lim_reg = '0, frame_len_lim_next;
logic [13:0] frame_len_lim_cyc_reg = '0, frame_len_lim_cyc_next;
logic [1:0] frame_len_lim_last_reg = '0, frame_len_lim_last_next;
logic frame_len_lim_check_reg = '0, frame_len_lim_check_next;
logic [DATA_W-1:0] m_axis_rx_tdata_reg = '0, m_axis_rx_tdata_next;
logic [KEEP_W-1:0] m_axis_rx_tkeep_reg = '0, m_axis_rx_tkeep_next;
@@ -231,7 +233,9 @@ always_comb begin
is_bcast_next = is_bcast_reg;
is_8021q_next = is_8021q_reg;
frame_len_next = frame_len_reg;
frame_len_lim_next = frame_len_lim_reg;
frame_len_lim_cyc_next = frame_len_lim_cyc_reg;
frame_len_lim_last_next = frame_len_lim_last_reg;
frame_len_lim_check_next = frame_len_lim_check_reg;
m_axis_rx_tdata_next = xgmii_rxd_d2;
m_axis_rx_tkeep_next = {KEEP_W{1'b1}};
@@ -275,10 +279,14 @@ always_comb begin
end
// counter for max frame length enforcement
if (frame_len_lim_reg[15:2] != 0) begin
frame_len_lim_next = frame_len_lim_reg - 16'(CTRL_W);
if (frame_len_lim_cyc_reg != 0) begin
frame_len_lim_cyc_next = frame_len_lim_cyc_reg - 1;
end else begin
frame_len_lim_next = '0;
frame_len_lim_cyc_next = '0;
end
if (frame_len_lim_cyc_reg == 2) begin
frame_len_lim_check_next = 1'b1;
end
// address and ethertype checks
@@ -303,8 +311,10 @@ always_comb begin
// idle state - wait for packet
reset_crc = 1'b1;
frame_oversize_next = 1'b0;
frame_len_next = 16'(CTRL_W);
frame_len_lim_next = cfg_rx_max_pkt_len;
{frame_len_lim_cyc_next, frame_len_lim_last_next} = cfg_rx_max_pkt_len;
frame_len_lim_check_next = 1'b0;
hdr_ptr_next = 0;
pre_ok_next = xgmii_rxd_d2[31:8] == 24'h555555;
@@ -330,7 +340,6 @@ always_comb begin
STATE_PREAMBLE: begin
// drop preamble
frame_len_lim_next = cfg_rx_max_pkt_len;
hdr_ptr_next = 0;
pre_ok_next = pre_ok_reg && xgmii_rxd_d2 == 32'hD5555555;
@@ -355,10 +364,17 @@ always_comb begin
if (term_present_reg) begin
stat_rx_byte_next = 3'(term_lane_reg);
frame_oversize_next = frame_len_lim_reg < 16'(4+4+term_lane_reg);
if (frame_len_lim_check_reg) begin
if (frame_len_lim_last_reg < term_lane_reg) begin
frame_oversize_next = 1'b1;
end
end
end else begin
stat_rx_byte_next = 3'(CTRL_W);
frame_oversize_next = frame_len_lim_reg < 4+4;
if (frame_len_lim_check_reg) begin
// at the limit but this isn't a termination character
frame_oversize_next = 1'b1;
end
end
if (framing_error_reg) begin
@@ -477,7 +493,9 @@ always_ff @(posedge clk) begin
is_bcast_reg <= is_bcast_next;
is_8021q_reg <= is_8021q_next;
frame_len_reg <= frame_len_next;
frame_len_lim_reg <= frame_len_lim_next;
frame_len_lim_cyc_reg <= frame_len_lim_cyc_next;
frame_len_lim_last_reg <= frame_len_lim_last_next;
frame_len_lim_check_reg <= frame_len_lim_check_next;
m_axis_rx_tdata_reg <= m_axis_rx_tdata_next;
m_axis_rx_tkeep_reg <= m_axis_rx_tkeep_next;