[PATCH 01/14] mtd: gpmi: change the BCH layout setting for large oob NAND

[sbabic at denx.de <sbabic@denx.de>]

> From: Ye Li <ye.li@nxp.com>
> The code change updated the NAND driver BCH ECC layout algorithm to
> support large oob size NAND chips(oob > 1024 bytes) and proposed a new
> way to set ECC layout.
> Current implementation requires each chunk size larger than oob size so
> the bad block marker (BBM) can be guaranteed located in data chunk. The
> ECC layout always using the unbalanced layout(Ecc for both meta and
> Data0 chunk), but for the NAND chips with oob larger than 1k, the driver
> cannot support because BCH doesn?t support GF 15 for 2K chunk.
> The change keeps the data chunk no larger than 1k and adjust the ECC
> strength or ECC layout to locate the BBM in data chunk. General idea for
> large oob NAND chips is
> 1.Try all ECC strength from the minimum value required by NAND spec to
> the maximum one that works, any ECC makes the BBM locate in data chunk
> can be chosen.
> 2.If none of them works, using separate ECC for meta, which will add one
> extra ecc with the same ECC strength as other data chunks. This extra
> ECC can guarantee BBM located in data chunk, of course, we need to check
> if oob can afford it.
> Previous code has two methods for ECC layout setting, the
> legacy_calc_ecc_layout and calc_ecc_layout_by_info, the difference
> between these two methods is, legacy_calc_ecc_layout set the chunk size
> larger chan oob size and then set the maximum ECC strength that oob can
> afford. While the calc_ecc_layout_by_info set chunk size and ECC
> strength according to NAND spec. It has been proved that the first
> method cannot provide safe ECC strength for some modern NAND chips, so
> in current code,
> 1. Driver read NAND parameters first and then chose the proper ECC
> layout setting method.
> 2. If the oob is large or NAND required data chunk larger than oob size,
> chose calc_ecc_for_large_oob, otherwise use calc_ecc_layout_by_info
> 3. legacy_calc_ecc_layout only used for some NAND chips does not contains
> necessary information. So this is only a backup plan, it is NOT
> recommended to use these NAND chips.
> Signed-off-by: Han Xu <b45815@freescale.com>
> Signed-off-by: Ye Li <ye.li@nxp.com>
> Signed-off-by: Peng Fan <peng.fan@nxp.com>
Applied to u-boot-imx, master, thanks !

Best regards,
Stefano Babic

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