tools: kwboot: Improve retrying logic for incomplete xmodem packets

Sometimes if the first byte of xmodem packet (SOH) is incorrectly
transmitted, BootROM sends NAK for every non-SOH received byte, which
makes BootROM and the host kwboot tool out of sync. BootROM automatically
re-synchronizes after 2s pause by dropping its input queue. So when
attempting retransmit for 9th time or later, ignore NAK reply from BootROM
and either wait for valid ACK or let kwboot timeout, which implies
re-synchronization.

This fixes retransmission of xmodem packets and allows kwboot to work also
without "Waiting ... and flushing tty" code which is at the beginning of
kwboot xmodem transfer.

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>

diff --git a/tools/kwboot.c b/tools/kwboot.c
index 1477c0f..be9a751 100644 (file)
--- a/tools/kwboot.c
+++ b/tools/kwboot.c
@@ -880,6 +880,7 @@ kwboot_baud_magic_handle(int fd, char c, int baudrate)
 
 static int
 kwboot_xm_recv_reply(int fd, char *c, int nak_on_non_xm,
+                    int ignore_nak_reply,
                     int allow_non_xm, int *non_xm_print,
                     int baudrate, int *baud_changed)
 {
@@ -899,8 +900,14 @@ kwboot_xm_recv_reply(int fd, char *c, int nak_on_non_xm,
                }
 
                /* If received xmodem reply, end. */
-               if (_is_xm_reply(*c))
+               if (_is_xm_reply(*c)) {
+                       if (*c == NAK && ignore_nak_reply) {
+                               timeout = recv_until - _now();
+                               if (timeout >= 0)
+                                       continue;
+                       }
                        break;
+               }
 
                /*
                 * If receiving/printing non-xmodem text output is allowed and
@@ -968,6 +975,7 @@ kwboot_xm_sendblock(int fd, struct kwboot_block *block, int allow_non_xm,
                }
 
                rc = kwboot_xm_recv_reply(fd, &c, retries < 3,
+                                         retries > 8,
                                          allow_non_xm, &non_xm_print,
                                          baudrate, &baud_changed);
                if (rc)
@@ -1011,6 +1019,7 @@ kwboot_xm_finish(int fd)
                        return rc;
 
                rc = kwboot_xm_recv_reply(fd, &c, retries < 3,
+                                         retries > 8,
                                          0, NULL, 0, NULL);
                if (rc)
                        return rc;