From f21e9797a28b6f4eb84f6c3a74d3b64817abc42a Mon Sep 17 00:00:00 2001
From: jaseg <git@jaseg.de>
Date: Sun, 1 May 2022 17:24:19 +0200
Subject: Fix 8b10b encoding running disparity issues.

---
 common/8b10b.c | 39 +++++++++++++++++++++++++--------------
 1 file changed, 25 insertions(+), 14 deletions(-)

(limited to 'common')

diff --git a/common/8b10b.c b/common/8b10b.c
index a32b7f2..fd89e6f 100644
--- a/common/8b10b.c
+++ b/common/8b10b.c
@@ -139,20 +139,24 @@ static const int8_t map_4b3b[16] = {
 };
 
 static const uint16_t k_sym_map[K_CODES_LAST] = {
-    [K28_0] = 0b0011110100,
-    [K28_1] = 0b0011111001,
-    [K28_2] = 0b0011110101,
-    [K28_3] = 0b0011110011,
-    [K28_4] = 0b0011110010,
-    [K28_5] = 0b0011111010,
-    [K28_6] = 0b0011110110,
-    [K28_7] = 0b0011111000,
-    [K23_7] = 0b1110101000,
-    [K27_7] = 0b1101101000,
-    [K29_7] = 0b1011101000,
-    [K30_7] = 0b0111101000
+    [K28_0] = 0b0011110100, /* rd =  0 */
+    [K28_1] = 0b0011111001, /* rd = +2 */
+    [K28_2] = 0b0011110101, /* rd = +2 */
+    [K28_3] = 0b0011110011, /* rd = +2 */
+    [K28_4] = 0b0011110010, /* rd =  0 */
+    [K28_5] = 0b0011111010, /* rd = +2 */
+    [K28_6] = 0b0011110110, /* rd = +2 */
+    [K28_7] = 0b0011111000, /* rd =  0 */
+    [K23_7] = 0b1110101000, /* rd =  0 */
+    [K27_7] = 0b1101101000, /* rd =  0 */
+    [K29_7] = 0b1011101000, /* rd =  0 */
+    [K30_7] = 0b0111101000  /* rd =  0 */
 };
 
+static const uint16_t k_sym_rd =
+    (1<<K28_1) | (1<<K28_2) | (1<<K28_3) | (1<<K28_5) | (1<<K28_6);
+
+
 void xfr_8b10b_reset(struct state_8b10b_dec *st) {
     st->rx = 0;
     st->bit_ctr = 0; /* unsynchronized */
@@ -199,11 +203,19 @@ void xfr_8b10b_encode_reset(struct state_8b10b_enc *st) {
 }
 
 int xfr_8b10b_encode(struct state_8b10b_enc *st, int data) {
+    if (st->rd != -1 && st->rd != 1)
+        return -EINVAL;
+
     if (data < 0) {
         if (-data >= sizeof(k_sym_map)/sizeof(k_sym_map[0]))
             return -EINVAL;
 
-        return k_sym_map[-data];
+        int sym = k_sym_map[-data];
+        if (st->rd > 0)
+            sym = (~sym) & 0x3ff;
+        if ((k_sym_rd >> (-data)) & 0x1)
+            st->rd = -st->rd;
+        return sym;
     }
 
     if (data > 255)
@@ -215,7 +227,6 @@ int xfr_8b10b_encode(struct state_8b10b_enc *st, int data) {
     int x5b = (st->rd == -1) ?  map_5b6b[p5b].rd_neg : map_5b6b[p5b].rd_pos;
     st->rd -= map_5b6b[p5b].disp * st->rd;
     //fprintf(stderr, "\nnow: rd %d data %x p5b %d p3b %d\n", st->rd, data, p5b, p3b);
-    //assert(st->rd == -1 || st->rd == 1);
 
     int x3b = (st->rd == -1) ?  map_3b4b_d[p3b].rd_neg : map_3b4b_d[p3b].rd_pos;
     if (p3b == 7) {
-- 
cgit