Thanks to Johannes Sjölund for reporting that the Bus Pirate init could

not deal with a Bus Pirate which is already in binary Bitbang mode. This
is caused by a combination of the slowness of the Bus Pirate, the
slowness of USB and a fast serial port flush routine which just flushes
the buffer contents and does not wait until data arrival stops.

Make the Bus Pirate init more robust by running the flush command 10
times with 1.5 ms delay in between.

This code development was sponsored by Mattias Mattsson. Thanks!
Tested a few dozen times, should work reliably.

Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Acked-by: Mattias Mattsson <vitplister@gmail.com>


git-svn-id: https://code.coreboot.org/svn/flashrom/trunk@1178 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1

1 files changed, 21 insertions, 0 deletions

diff --git a/buspirate_spi.c b/buspirate_spi.c
index c56155f..9890d48 100644
--- a/buspirate_spi.c
+++ b/buspirate_spi.c
@@ -22,6 +22,7 @@
 #include <string.h>
 #include <stdlib.h>
 #include <ctype.h>
+#include <unistd.h>
 #include "flash.h"
 #include "chipdrivers.h"
 #include "programmer.h"
@@ -141,6 +142,20 @@ int buspirate_spi_init(void)
 		/* Read any response and discard it. */
 		sp_flush_incoming();
 	}
+	/* USB is slow. The Bus Pirate is even slower. Apparently the flush
+	 * action above is too fast or too early. Some stuff still remains in
+	 * the pipe after the flush above, and one additional flush is not
+	 * sufficient either. Use a 1.5 ms delay inside the loop to make
+	 * mostly sure that at least one USB frame had time to arrive.
+	 * Looping only 5 times is not sufficient and causes the
+	 * ocassional failure.
+	 * Folding the delay into the loop above is not reliable either.
+	 */
+	for (i = 0; i < 10; i++) {
+		usleep(1500);
+		/* Read any response and discard it. */
+		sp_flush_incoming();
+	}
 	/* Enter raw bitbang mode */
 	buf[0] = 0x00;
 	ret = buspirate_sendrecv(buf, 1, 5);
@@ -148,6 +163,8 @@ int buspirate_spi_init(void)
 		return ret;
 	if (memcmp(buf, "BBIO", 4)) {
 		msg_perr("Entering raw bitbang mode failed!\n");
+		msg_pdbg("Got %02x%02x%02x%02x%02x\n",
+			 buf[0], buf[1], buf[2], buf[3], buf[4]);
 		return 1;
 	}
 	msg_pdbg("Raw bitbang mode version %c\n", buf[4]);
@@ -159,8 +176,12 @@ int buspirate_spi_init(void)
 	/* Enter raw SPI mode */
 	buf[0] = 0x01;
 	ret = buspirate_sendrecv(buf, 1, 4);
+	if (ret)
+		return ret;
 	if (memcmp(buf, "SPI", 3)) {
 		msg_perr("Entering raw SPI mode failed!\n");
+		msg_pdbg("Got %02x%02x%02x%02x\n",
+			 buf[0], buf[1], buf[2], buf[3]);
 		return 1;
 	}
 	msg_pdbg("Raw SPI mode version %c\n", buf[3]);