Pretty much everybody who used the FT2232 SPI driver in flashrom had problems with incorrect reads from time to time

One reason was that the hardware is pretty timing sensitive even for reads.
The other reason was that the code silently ignored errors. This patch doesn't
add any error recovery, but it will emit error messages if FT2232 communication
goes wrong. That allows us to track down errors without investing hours in
driver debugging. Thanks to Jeremy Buseman <naviathan@gmail.com> for testing.
He found out that certain libftdi/libusb/kernel/hardware combinations drop
some bytes without returning any error codes.

Corresponding to flashrom svn r769.

Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Acked-by: Paul Fox <pgf@laptop.org>

1 files changed, 16 insertions, 4 deletions

diff --git a/ft2232_spi.c b/ft2232_spi.c
index 17930eb..aa00753 100644
--- a/ft2232_spi.c
+++ b/ft2232_spi.c
@@ -198,7 +198,8 @@ int ft2232_spi_send_command(unsigned int writecnt, unsigned int readcnt,
 {
 	struct ftdi_context *ftdic = &ftdic_context;
 	static unsigned char *buf = NULL;
-	int i = 0, ret = 0;
+	/* failed is special. We use bitwise ops, but it is essentially bool. */
+	int i = 0, ret = 0, failed = 0;
 
 	if (writecnt > 65536 || readcnt > 65536)
 		return SPI_INVALID_LENGTH;
@@ -237,6 +238,11 @@ int ft2232_spi_send_command(unsigned int writecnt, unsigned int readcnt,
 		buf[i++] = (readcnt - 1) & 0xff;
 		buf[i++] = ((readcnt - 1) >> 8) & 0xff;
 		ret = send_buf(ftdic, buf, i);
+		failed = ret;
+		/* We can't abort here, we still have to deassert CS#. */
+		if (ret)
+			fprintf(stderr, "send_buf failed before read: %i\n",
+				ret);
 		i = 0;
 		if (ret == 0) {
 			/*
@@ -245,6 +251,10 @@ int ft2232_spi_send_command(unsigned int writecnt, unsigned int readcnt,
 			 * command. We may be scheduled out etc.
 			 */
 			ret = get_buf(ftdic, readarr, readcnt);
+			failed |= ret;
+			/* We can't abort here either. */
+			if (ret)
+				fprintf(stderr, "get_buf failed: %i\n", ret);
 		}
 	}
 
@@ -252,10 +262,12 @@ int ft2232_spi_send_command(unsigned int writecnt, unsigned int readcnt,
 	buf[i++] = SET_BITS_LOW;
 	buf[i++] = CS_BIT;
 	buf[i++] = 0x0b;
-	if (send_buf(ftdic, buf, i))
-		return -1;
+	ret = send_buf(ftdic, buf, i);
+	failed |= ret;
+	if (ret)
+		fprintf(stderr, "send_buf failed at end: %i\n", ret);
 
-	return ret;
+	return failed ? -1 : 0;
 }
 
 int ft2232_spi_read(struct flashchip *flash, uint8_t *buf, int start, int len)