[PATCH u-boot-marvell 06/14] tools: kwboot: Fix handling of repeated xmodem packets

[Marek Behún]

From: Pali Rohár <pali at kernel.org>

Unfortunately during some stages of xmodem transfer, A385 BootROM is not
able to handle repeated xmodem packets. So if an error occurs during that
stage, stop the transfer and return failure.

Signed-off-by: Pali Rohár <pali at kernel.org>
Signed-off-by: Marek Behún <marek.behun at nic.cz>
---
 tools/kwboot.c | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/tools/kwboot.c b/tools/kwboot.c
index a619a6c3c1..dfac8aed7b 100644
--- a/tools/kwboot.c
+++ b/tools/kwboot.c
@@ -946,7 +946,7 @@ kwboot_xm_recv_reply(int fd, char *c, int stop_on_non_xm,
 
 static int
 kwboot_xm_sendblock(int fd, struct kwboot_block *block, int allow_non_xm,
-		    int *done_print, int baudrate)
+		    int *done_print, int baudrate, int allow_retries)
 {
 	int non_xm_print, baud_changed;
 	int rc, err, retries;
@@ -977,7 +977,7 @@ kwboot_xm_sendblock(int fd, struct kwboot_block *block, int allow_non_xm,
 
 		if (!allow_non_xm && c != ACK)
 			kwboot_progress(-1, '+');
-	} while (c == NAK && retries++ < 16);
+	} while (c == NAK && allow_retries && retries++ < 16);
 
 	if (non_xm_print)
 		kwboot_printv("\n");
@@ -1044,8 +1044,30 @@ kwboot_xmodem_one(int tty, int *pnum, int header, const uint8_t *data,
 
 		last_block = (left <= blksz);
 
+		/*
+		 * Handling of repeated xmodem packets is completely broken in
+		 * Armada 385 BootROM - it completely ignores xmodem packet
+		 * numbers, they are only used for checksum verification.
+		 * BootROM can handle a retry of the xmodem packet only during
+		 * the transmission of kwbimage header and only if BootROM
+		 * itself sent NAK response to previous attempt (it does it on
+		 * checksum failure). During the transmission of kwbimage data
+		 * part, BootROM always expects next xmodem packet, even if it
+		 * sent NAK to previous attempt - there is absolutely no way to
+		 * repair incorrectly transmitted xmodem packet during kwbimage
+		 * data part upload. Also, if kwboot receives non-ACK/NAK
+		 * response (meaning that original BootROM response was damaged
+		 * on UART) there is no way to detect if BootROM accepted xmodem
+		 * packet or not and no way to check if kwboot could repeat the
+		 * packet or not.
+		 *
+		 * Stop transfer and return failure if kwboot receives unknown
+		 * reply if non-xmodem reply is not allowed (for all xmodem
+		 * packets except the last header packet) or when non-ACK reply
+		 * is received during data part transfer.
+		 */
 		rc = kwboot_xm_sendblock(tty, &block, header && last_block,
-					 &done_print, baudrate);
+					 &done_print, baudrate, header);
 		if (rc)
 			goto out;
 
-- 
2.34.1