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[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>
This commit is contained in:
Ben Dooks 2008-04-14 14:58:58 +01:00 committed by David Woodhouse
parent 37e5ffa3f1
commit ed8165c75e
1 changed files with 21 additions and 0 deletions
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21
drivers/mtd/nand/nand_base.c
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@ -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) {