[MTD] [NAND] Verify probe by retrying to checking the results match
With modern systems using bus-hold instead of bus pull-up, it can
often lead to erroneous reporting of NAND devices where there are
none. Do a double probe to ensure that the result we got the first
time is repeatable, and if it is not then return that there is no
chip there.
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 7acb1a0..ba1bdf7 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -2229,6 +2229,7 @@
{
struct nand_flash_dev *type = NULL;
int i, dev_id, maf_idx;
+ int tmp_id, tmp_manf;
/* Select the device */
chip->select_chip(mtd, 0);
@@ -2240,6 +2241,26 @@
*maf_id = chip->read_byte(mtd);
dev_id = chip->read_byte(mtd);
+ /* Try again to make sure, as some systems the bus-hold or other
+ * interface concerns can cause random data which looks like a
+ * possibly credible NAND flash to appear. If the two results do
+ * not match, ignore the device completely.
+ */
+
+ chip->cmdfunc(mtd, NAND_CMD_READID, 0x00, -1);
+
+ /* Read manufacturer and device IDs */
+
+ tmp_manf = chip->read_byte(mtd);
+ tmp_id = chip->read_byte(mtd);
+
+ if (tmp_manf != *maf_id || tmp_id != dev_id) {
+ printk(KERN_INFO "%s: second ID read did not match "
+ "%02x,%02x against %02x,%02x\n", __func__,
+ *maf_id, dev_id, tmp_manf, tmp_id);
+ return ERR_PTR(-ENODEV);
+ }
+
/* Lookup the flash id */
for (i = 0; nand_flash_ids[i].name != NULL; i++) {
if (dev_id == nand_flash_ids[i].id) {