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.

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


git-svn-id: https://code.coreboot.org/svn/flashrom/trunk@769 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1

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)