From: Graeme Foot <graeme.foot@touchcut.com>
Date: Mon, 21 May 2018 11:07:00 +1200

Allow DC Sync1 offset to function

diff --git a/master/fsm_slave_config.c b/master/fsm_slave_config.c
--- a/master/fsm_slave_config.c
+++ b/master/fsm_slave_config.c
@@ -1379,7 +1379,8 @@
         // set DC cycle times
         ec_datagram_fpwr(datagram, slave->station_address, 0x09A0, 8);
         EC_WRITE_U32(datagram->data, config->dc_sync[0].cycle_time);
-        EC_WRITE_U32(datagram->data + 4, config->dc_sync[1].cycle_time);
+        EC_WRITE_U32(datagram->data + 4, config->dc_sync[1].cycle_time + 
+                config->dc_sync[1].shift_time);
         fsm->retries = EC_FSM_RETRIES;
         fsm->state = ec_fsm_slave_config_state_dc_cycle;
     } else {
diff --git a/master/slave_config.c b/master/slave_config.c
--- a/master/slave_config.c
+++ b/master/slave_config.c
@@ -1000,8 +1000,33 @@
     sc->dc_assign_activate = assign_activate;
     sc->dc_sync[0].cycle_time = sync0_cycle_time;
     sc->dc_sync[0].shift_time = sync0_shift_time;
-    sc->dc_sync[1].cycle_time = sync1_cycle_time;
-    sc->dc_sync[1].shift_time = sync1_shift_time;
+    if (sync0_cycle_time > 0)
+    {
+      sc->dc_sync[1].shift_time = (sync1_cycle_time + sync1_shift_time) %
+              sync0_cycle_time;
+              
+      if ((sync1_cycle_time + sync1_shift_time) < sc->dc_sync[1].shift_time)
+      {
+        EC_CONFIG_ERR(sc, "Slave Config DC 0x%p results in a negative "
+              "sync1 cycle.  Resetting to zero cycle and shift time\n", 
+              sc);
+
+        sc->dc_sync[1].cycle_time = 0;
+        sc->dc_sync[1].shift_time = 0;
+      }
+      else
+      {
+        sc->dc_sync[1].cycle_time = (sync1_cycle_time + sync1_shift_time) -
+                sc->dc_sync[1].shift_time;
+      }
+    }
+    else
+    {
+      sc->dc_sync[0].cycle_time = sync1_cycle_time;
+      sc->dc_sync[0].shift_time += sync1_shift_time;
+      sc->dc_sync[1].cycle_time = 0;
+      sc->dc_sync[1].shift_time = 0;
+    }
 }
 
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