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axis_mii_tx: Simplify backoff 

We only care about backoff when state=BACKOFF. We can simplify the
calculation by defaulting to loading lfsr into backoff, and special
casing things for state=BACKOFF.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
This commit is contained in:
Sean Anderson 2023-01-11 00:52:51 -05:00
parent 19f2f656cd
commit aba4fb10c2
1 changed files with 14 additions and 14 deletions
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28
rtl/axis_mii_tx.v
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@ -197,8 +197,20 @@ module axis_mii_tx (
if (do_crc) if (do_crc)
crc_state_next = crc_state_out; crc_state_next = crc_state_out;
backoff_next = backoff;
lfsr_next = { lfsr[8:0], lfsr[9] ^ lfsr[6] }; lfsr_next = { lfsr[8:0], lfsr[9] ^ lfsr[6] };
case (retries)
15: backoff_next = lfsr[ 0];
14: backoff_next = lfsr[1:0];
13: backoff_next = lfsr[2:0];
12: backoff_next = lfsr[3:0];
11: backoff_next = lfsr[4:0];
10: backoff_next = lfsr[5:0];
9: backoff_next = lfsr[6:0];
8: backoff_next = lfsr[7:0];
7: backoff_next = lfsr[8:0];
6, 5, 4, 3, 2, 1, 0:
backoff_next = lfsr[9:0];
endcase
odd_next = odd ^ mii_tx_ce_next; odd_next = odd ^ mii_tx_ce_next;
mii_tx_en_next = mii_tx_en; mii_tx_en_next = mii_tx_en;
@ -421,19 +433,6 @@ module axis_mii_tx (
state_counter_next = 0; state_counter_next = 0;
replay_next = 1; replay_next = 1;
retries_next = retries - 1; retries_next = retries - 1;
case (retries)
15: backoff_next = lfsr[ 0];
14: backoff_next = lfsr[1:0];
13: backoff_next = lfsr[2:0];
12: backoff_next = lfsr[3:0];
11: backoff_next = lfsr[4:0];
10: backoff_next = lfsr[5:0];
9: backoff_next = lfsr[6:0];
8: backoff_next = lfsr[7:0];
7: backoff_next = lfsr[8:0];
6, 5, 4, 3, 2, 1, 0:
backoff_next = lfsr[9:0];
endcase
end else begin end else begin
state_counter_next = IPG_BYTES - 1; state_counter_next = IPG_BYTES - 1;
if (state == JAM_FAIL) begin if (state == JAM_FAIL) begin
@ -462,6 +461,7 @@ module axis_mii_tx (
mii_tx_en_next = 0; mii_tx_en_next = 0;
end end
BACKOFF: begin BACKOFF: begin
backoff_next = backoff;
if (mii_tx_ce_next && odd) begin if (mii_tx_ce_next && odd) begin
mii_tx_en_next = 0; mii_tx_en_next = 0;
if (!state_counter) begin if (!state_counter) begin