command: Wait to send ack until after processing commands

Send the ack after processing commands - this gives the host code more
information on serial buffer utilization.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/chelper/serialqueue.c

@@ -363,7 +363,7 @@ struct serialqueue {
     double last_receive_sent_time;
     // Retransmit support
     uint64_t send_seq, receive_seq;
-    uint64_t ignore_nak_seq, retransmit_seq, rtt_sample_seq;
+    uint64_t ignore_nak_seq, last_ack_seq, retransmit_seq, rtt_sample_seq;
     struct list_head sent_queue;
     double srtt, rttvar, rto;
     // Pending transmission message queues
@@ -509,10 +509,14 @@ handle_message(struct serialqueue *sq, double eventtime, int len)
     if (rseq != sq->receive_seq)
         // New sequence number
         update_receive_seq(sq, eventtime, rseq);
-    else if (len == MESSAGE_MIN && rseq > sq->ignore_nak_seq
-             && !list_empty(&sq->sent_queue))
-        // Duplicate sequence number in an empty message is a nak
-        pollreactor_update_timer(&sq->pr, SQPT_RETRANSMIT, PR_NOW);
+    if (len == MESSAGE_MIN) {
+        // Ack/nak message
+        if (sq->last_ack_seq < rseq)
+            sq->last_ack_seq = rseq;
+        else if (rseq > sq->ignore_nak_seq && !list_empty(&sq->sent_queue))
+            // Duplicate Ack is a Nak - do fast retransmit
+            pollreactor_update_timer(&sq->pr, SQPT_RETRANSMIT, PR_NOW);
+    }
 
     if (len > MESSAGE_MIN) {
         // Add message to receive queue

src/command.c

@@ -257,7 +257,6 @@ command_find_block(uint8_t *buf, uint_fast8_t buf_len, uint_fast8_t *pop_count)
         goto nak;
     }
     next_sequence = ((msgseq + 1) & MESSAGE_SEQ_MASK) | MESSAGE_DEST;
-    command_sendf(&encode_acknak);
     return 1;
 
 need_more_data:
@@ -308,13 +307,22 @@ command_dispatch(uint8_t *buf, uint_fast8_t msglen)
     }
 }
 
+// Send an ack message to the host (notifying that it can send more data)
+void
+command_send_ack(void)
+{
+    command_sendf(&encode_acknak);
+}
+
 // Find a message block and then dispatch all the commands in it
 int_fast8_t
 command_find_and_dispatch(uint8_t *buf, uint_fast8_t buf_len
                           , uint_fast8_t *pop_count)
 {
     int_fast8_t ret = command_find_block(buf, buf_len, pop_count);
-    if (ret > 0)
+    if (ret > 0) {
         command_dispatch(buf, *pop_count);
+        command_send_ack();
+    }
     return ret;
 }

src/command.h

@@ -72,6 +72,7 @@ void command_sendf(const struct command_encoder *ce, ...);
 int_fast8_t command_find_block(uint8_t *buf, uint_fast8_t buf_len
                                , uint_fast8_t *pop_count);
 void command_dispatch(uint8_t *buf, uint_fast8_t msglen);
+void command_send_ack(void);
 int_fast8_t command_find_and_dispatch(uint8_t *buf, uint_fast8_t buf_len
                                       , uint_fast8_t *pop_count);
 

src/generic/serial_irq.c

@@ -75,8 +75,11 @@ console_task(void)
     int_fast8_t ret = command_find_block(receive_buf, rpos, &pop_count);
     if (ret > 0)
         command_dispatch(receive_buf, pop_count);
-    if (ret)
+    if (ret) {
         console_pop_input(pop_count);
+        if (ret > 0)
+            command_send_ack();
+    }
 }
 DECL_TASK(console_task);
 

src/pru/pru0.c

@@ -148,8 +148,10 @@ check_can_read(void)
         int_fast8_t ret = command_find_block(p, msglen, &pop_count);
         if (!ret)
             break;
-        if (ret > 0)
+        if (ret > 0) {
             do_dispatch(p, pop_count);
+            command_send_ack();
+        }
         p += pop_count;
         len -= pop_count;
     }