From 9de72c2e4f84b345b11b09e25de0ca6f2675340b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de>
Date: Sat, 11 Feb 2017 20:57:52 +0100
Subject: [PATCH] scripts/kwboot: new parameter -n to skip a number of NAKs
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On some machines the CPU resets twice and so kwboot must hit the second
window to enter debug or boot mode. For this scenario it helps to ignore
a number of NAKs. If you choose a number too high for booting, the process
is only slowed down because when the CPU enters UART boot mode it sends NAKs
when not getting any input.

This new option also helps when there are voltage fluctuations due to the
power up sequence which might be interpreted as valid chars.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 scripts/kwboot.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/scripts/kwboot.c b/scripts/kwboot.c
index 3ab26cd93..4c6b19aa2 100644
--- a/scripts/kwboot.c
+++ b/scripts/kwboot.c
@@ -264,10 +264,11 @@ out:
 }
 
 static int
-kwboot_bootmsg(int tty, void *msg)
+kwboot_bootmsg(int tty, void *msg, unsigned num_nacks)
 {
 	int rc;
 	char c;
+	unsigned saw_nacks = 0;
 
 	if (msg == NULL)
 		kwboot_printv("Please reboot the target into UART boot mode...");
@@ -295,11 +296,13 @@ kwboot_bootmsg(int tty, void *msg)
 				kwboot_printv("\\x%02hhx", c);
 
 			rc = kwboot_tty_recv(tty, &c, 1, KWBOOT_MSG_RSP_TIMEO);
+
+			saw_nacks = 0;
 		}
 
-	} while (rc || c != NAK);
+	} while (rc || c != NAK || (++saw_nacks < num_nacks));
 
-	kwboot_printv("\nGot expected NAK\n");
+	kwboot_printv("\nGot expected NAKs\n");
 
 	return rc;
 }
@@ -736,6 +739,7 @@ main(int argc, char **argv)
 	void *bootmsg;
 	void *debugmsg;
 	void *img;
+	unsigned num_nacks = 1;
 	size_t size;
 	speed_t speed;
 
@@ -752,7 +756,7 @@ main(int argc, char **argv)
 	kwboot_verbose = isatty(STDOUT_FILENO);
 
 	do {
-		int c = getopt(argc, argv, "b:dfhtB:D:");
+		int c = getopt(argc, argv, "b:dfhtn:B:D:");
 		if (c < 0)
 			break;
 
@@ -779,6 +783,10 @@ main(int argc, char **argv)
 			force = 1;
 			break;
 
+		case 'n':
+			num_nacks = atoi(optarg);
+			break;
+
 		case 'B':
 			speed = kwboot_tty_speed(atoi(optarg));
 			if (speed == -1)
@@ -828,7 +836,7 @@ main(int argc, char **argv)
 			goto out;
 		}
 	} else {
-		rc = kwboot_bootmsg(tty, bootmsg);
+		rc = kwboot_bootmsg(tty, bootmsg, num_nacks);
 		if (rc) {
 			perror("bootmsg");
 			goto out;