skywater
/
ethernet
mirror of https://github.com/Forty-Bot/ethernet.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

axis_mii_tx: Delay error handling by one cycle 

The 2 ns delay when reading from a BRAM makes it hard to close timing,
since buf_err affects the state machine. Address this by not acting on
errors for a clock cycle. We will output bad data for a cycle, but we
are going to corrupt the FCS anyway so it doesn't matter. We also have
to check for errors in the PAD/FCS states, to ensure they don't slip
past.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
This commit is contained in:
Sean Anderson 2023-01-11 17:32:50 -05:00
parent 01ff073916
commit 536bdd86bd
1 changed files with 32 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

41
rtl/axis_mii_tx.v
View File

@ -182,7 +182,7 @@ module axis_mii_tx (
reg [5:0] state_counter, state_counter_next;
reg [9:0] lfsr, lfsr_next, backoff, backoff_next;
reg transmit_ok_next, gave_up_next, late_collision_next;
reg underflow_next;
reg underflow_next, err, err_next;
always @(*) begin
mii_tx_ce_next_next_next = 0;
@ -223,6 +223,10 @@ module axis_mii_tx (
state_counter_next = state_counter - 1;
end
err_next = 0;
if (buf_ready && buf_valid && buf_err)
err_next = 1;
transmit_ok_next = 0;
gave_up_next = 0;
late_collision_next = 0;
@ -319,18 +323,13 @@ module axis_mii_tx (
end
endcase
if (!buf_valid || buf_err) begin
if (buf_valid && buf_last)
if (!buf_valid) begin
if (buf_last)
state_next = JAM_FAIL;
else
state_next = JAM_DRAIN;
/*
* Start jamming immediately to avoid
* sending Xs
*/
state_counter_next = JAM_BYTES - 2;
data_next = DATA_JAM;
state_counter_next = JAM_BYTES - 1;
underflow_next = 1;
if (state == DATA_EARLY)
done_next = 1;
@ -351,6 +350,14 @@ module axis_mii_tx (
state_counter_next = JAM_BYTES - 1;
end
end
if (err) begin
state_next = JAM_DRAIN;
state_counter_next = JAM_BYTES - 1;
underflow_next = 1;
if (state == DATA_EARLY)
done_next = 1;
end
end
PAD_EARLY,
PAD_LATE: begin
@ -378,6 +385,14 @@ module axis_mii_tx (
end
end
end
if (err) begin
state_next = JAM_FAIL;
state_counter_next = JAM_BYTES - 1;
underflow_next = 1;
if (state == PAD_EARLY)
done_next = 1;
end
end
FCS: begin
if (do_state) begin
@ -398,6 +413,12 @@ module axis_mii_tx (
transmit_ok_next = 0;
end
end
if (err) begin
state_next = JAM_FAIL;
state_counter_next = JAM_BYTES - 1;
underflow_next = 1;
end
end
IPG_OR_JAM: begin
if (do_state) begin
@ -499,6 +520,7 @@ module axis_mii_tx (
late_collision <= 0;
underflow <= 0;
buf_ready <= 0;
err <= 0;
done <= 0;
replay <= 0;
end else begin
@ -513,6 +535,7 @@ module axis_mii_tx (
state <= state_next;
state_counter <= state_counter_next;
buf_ready <= buf_ready_next;
err <= err_next;
data <= data_next;
replay <= replay_next;
done <= done_next;