From ed8165c75e3dd0b2e51b92a858cabe29ba00c9cb Mon Sep 17 00:00:00 2001 From: Ben Dooks Date: Mon, 14 Apr 2008 14:58:58 +0100 Subject: [PATCH] [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 Signed-off-by: David Woodhouse --- drivers/mtd/nand/nand_base.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c index 7acb1a0e7409..ba1bdf787323 100644 --- a/drivers/mtd/nand/nand_base.c +++ b/drivers/mtd/nand/nand_base.c @@ -2229,6 +2229,7 @@ static struct nand_flash_dev *nand_get_flash_type(struct mtd_info *mtd, { 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 @@ static struct nand_flash_dev *nand_get_flash_type(struct mtd_info *mtd, *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) { -- 2.20.1