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mtd: nand: fix Samsung SLC NAND identification regression 

A combination of the following two commits caused a regression in 3.7-rc1
when identifying some Samsung NAND, so that some previously working NAND
were no longer detected properly:

    commit e3b88bd604
    mtd: nand: add generic READ ID length calculation functions

    commit e2d3a35ee4
    mtd: nand: detect Samsung K9GBG08U0A, K9GAG08U0F ID

Particularly, a regression was seen on Samsung K9F2G08U0B, with the
following full 8-byte READ ID string:

    ec da 10 95 44 00 ec da

The basic problem is that Samsung manufactures both SLC and MLC NAND
that use a non-standard decoding table for deriving information from
their IDs. I have heuristically determined that all the chips that use
the new table have ID strings which wrap around after the 6th byte.
Unfortunately, I overlooked the fact that some older Samsung SLC (which
use a different decoding table) have "5 byte ID strings" which also wrap
around after the 6th byte.

This patch re-introduces a distinction between these old and new Samsung
NAND by checking that the 6th byte is non-zero, allowing both old and
new Samsung NAND to be detected properly.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Tested-by: Brian Norris <computersforpeace@gmail.com>
Reported-by: Marek Vasut <marex@denx.de>
Tested-by: Marek Vasut <marex@denx.de>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
This commit is contained in:
Brian Norris 2012-10-09 23:26:06 -07:00 committed by Artem Bityutskiy
parent 5ffd3412ae
commit af451af4e0
1 changed files with 5 additions and 4 deletions
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9
drivers/mtd/nand/nand_base.c
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@ -2983,13 +2983,14 @@ static void nand_decode_ext_id(struct mtd_info *mtd, struct nand_chip *chip,
/*
* Field definitions are in the following datasheets:
* Old style (4,5 byte ID): Samsung K9GAG08U0M (p.32)
* New style (6 byte ID): Samsung K9GAG08U0F (p.44)
* New Samsung (6 byte ID): Samsung K9GAG08U0F (p.44)
* Hynix MLC (6 byte ID): Hynix H27UBG8T2B (p.22)
*
* Check for ID length, cell type, and Hynix/Samsung ID to decide what
* to do.
* Check for ID length, non-zero 6th byte, cell type, and Hynix/Samsung
* ID to decide what to do.
*/
if (id_len == 6 && id_data[0] == NAND_MFR_SAMSUNG) {
if (id_len == 6 && id_data[0] == NAND_MFR_SAMSUNG &&
id_data[5] != 0x00) {
/* Calc pagesize */
mtd->writesize = 2048 << (extid & 0x03);
extid >>= 2;