mtd: nand: detect OOB size for Toshiba 24nm raw SLC
Toshiba NAND datasheets have not been very forthcoming on OOB size
information; they do not provide any bitfields in the ID string for
spare area. In their 24nm technology flash, however, Toshiba migrated
their NAND to have 32 bytes spare per 512 bytes of page area (up from
the traditional 16 bytes), as they now require 8-bit ECC or higher.
I have discussed this issue directly with Toshiba representatives, and
they acknowledge this problem. They recommend detecting these flash
based on their technology node as follows:
For 24nm Toshiba SLC raw NAND (not BENAND -- Built-in Ecc NAND), there
are 32 bytes of spare area for every 512 bytes of in-band data area.
We can implement this rule with the following snippet of a device ID
decode table, which applies to all their 43nm, 32nm, and 24nm SLC NAND
(this table is not fully in the NAND datasheets, but it was provided
directly by Toshiba representatives):