tree 9ea8dd919906f66718739b70c5b6e2a93441ac71
parent d6b6303dbe00f99d105f1d4479f6ea60434861c1
author Peng Fan <Peng.Fan@freescale.com> 1437466519 +0800
committer Scott Wood <scottwood@freescale.com> 1440561238 -0500

mtd: nand: mxs support oobsize bigger than 512

If ecc chunk data size is 512 and oobsize is bigger than 512, there is
a chance that block_mark_bit_offset conflicts with bch ecc area.

The following graph is modified from kernel gpmi-nand.c driver with
each data block 512 bytes. We can see that Block Mark conflicts with
ecc area from bch view. We can enlarge the ecc chunk size to avoid
this problem to those oobsize which is larger than 512.

   |                          P                                        |
   |<----------------------------------------------------------------->|
   |                                                                   |
   |                                                (Block Mark)       |
   |                      P'                             |           | |   |
   |<--------------------------------------------------->|     D     | | O'|
   |                                                     |<--------->| |<->|
   V                                                     V           V V   V
   +---+--------------+-+--------------+-+--------------+-+----------+-+---+
   | M |   data       |E|   data       |E|   data       |E|   data   |E|   |
   +---+--------------+-+--------------+-+--------------+-+----------+-+---+
                                                        ^                  ^
                                                        |         O        |
                                                        |<---------------->|

       P : the page size for BCH module.
       E : The ECC strength.
       G : the length of Galois Field.
       N : The chunk count of per page.
       M : the metasize of per page.
       C : the ecc chunk size, aka the "data" above.
       P': the nand chip's page size.
       O : the nand chip's oob size.
       O': the free oob.

Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Tested-By: Tim Harvey <tharvey@gateworks.com>