Check probing results for flash contents

When flashrom JEDEC code sends the ID command to the chip, it expects to
see IDs in the default flash location.

However, sometimes the chip does not react to the ID command, either
because it doesn't understand the command or because the command never
reached it. One way to detect this is to compare ID output with flash
chip contents for the same location. If they are identical, there is a
high chance you're not actually seeing ID output. Warn the user in that
case.

This patch helps a lot when a chip is not recognized and we want to
check if the probe responses are real IDs or just random flash chip
contents.

This should probably be added to all probe functions, but probe_jedec
is called for all sizes and thus flashrom will check this condition at
least once per size, making sure we can cross-match the warning.

Corresponding to flashrom svn r494.

Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Acked-by: FENG Yu Ning <fengyuning1984@gmail.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/jedec.c b/jedec.c
index ac6095b..bfbd93e 100644
--- a/jedec.c
+++ b/jedec.c
@@ -92,6 +92,7 @@ int probe_jedec(struct flashchip *flash)
 	volatile uint8_t *bios = flash->virtual_memory;
 	uint8_t id1, id2;
 	uint32_t largeid1, largeid2;
+	uint32_t flashcontent1, flashcontent2;
 
 	/* Issue JEDEC Product ID Entry command */
 	chip_writeb(0xAA, bios + 0x5555);
@@ -133,6 +134,26 @@ int probe_jedec(struct flashchip *flash)
 	printf_debug("%s: id1 0x%02x, id2 0x%02x", __FUNCTION__, largeid1, largeid2);
 	if (!oddparity(id1))
 		printf_debug(", id1 parity violation");
+
+	/* Read the product ID location again. We should now see normal flash contents. */
+	flashcontent1 = chip_readb(bios);
+	flashcontent2 = chip_readb(bios + 0x01);
+
+	/* Check if it is a continuation ID, this should be a while loop. */
+	if (flashcontent1 == 0x7F) {
+		flashcontent1 <<= 8;
+		flashcontent1 |= chip_readb(bios + 0x100);
+	}
+	if (flashcontent2 == 0x7F) {
+		flashcontent2 <<= 8;
+		flashcontent2 |= chip_readb(bios + 0x101);
+	}
+
+	if (largeid1 == flashcontent1)
+		printf_debug(", id1 is normal flash content");
+	if (largeid2 == flashcontent2)
+		printf_debug(", id2 is normal flash content");
+
 	printf_debug("\n");
 	if (largeid1 == flash->manufacture_id && largeid2 == flash->model_id)
 		return 1;