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diff --git a/doc/README.atmel_pmecc b/doc/README.atmel_pmecc new file mode 100644 index 0000000..b483744 --- /dev/null +++ b/doc/README.atmel_pmecc @@ -0,0 +1,44 @@ +How to enable PMECC(Programmable Multibit ECC) for nand on Atmel SoCs +----------------------------------------------------------- +2012-08-22 Josh Wu <josh.wu@atmel.com> + +The Programmable Multibit ECC (PMECC) controller is a programmable binary +BCH(Bose, Chaudhuri and Hocquenghem) encoder and decoder. This controller +can be used to support both SLC and MLC NAND Flash devices. It supports to +generate ECC to correct 2, 4, 8, 12 or 24 bits of error per sector (512 or +1024 bytes) of data. + +Following Atmel AT91 products support PMECC. +- AT91SAM9X25, X35, G25, G15, G35 (tested) +- AT91SAM9N12 (not tested, Should work) + +As soon as your nand flash software ECC works, you can enable PMECC. + +To use PMECC in this driver, the user needs to set: + 1. the PMECC correction error bits capability: CONFIG_PMECC_CAP. + It can be 2, 4, 8, 12 or 24. + 2. The PMECC sector size: CONFIG_PMECC_SECTOR_SIZE. + It only can be 512 or 1024. + 3. The PMECC index lookup table's offsets in ROM code: CONFIG_PMECC_INDEX_TABLE_OFFSET. + In the chip datasheet section "Boot Stragegies", you can find + two Galois Field Table in the ROM code. One table is for 512-bytes + sector. Another is for 1024-byte sector. Each Galois Field includes + two sub-table: indext table & alpha table. + In the beginning of each Galois Field Table is the index table, + Alpha table is in the following. + So the index table's offset is same as the Galois Field Table. + + Please set CONFIG_PMECC_INDEX_TABLE_OFFSET correctly according the + Galois Field Table's offset base on the sector size you used. + +Take AT91SAM9X5EK as an example, the board definition file likes: + +/* PMECC & PMERRLOC */ +#define CONFIG_ATMEL_NAND_HWECC 1 +#define CONFIG_ATMEL_NAND_HW_PMECC 1 +#define CONFIG_PMECC_CAP 2 +#define CONFIG_PMECC_SECTOR_SIZE 512 +#define CONFIG_PMECC_INDEX_TABLE_OFFSET 0x8000 + +NOTE: If you use 1024 as the sector size, then need set 0x10000 as the + CONFIG_PMECC_INDEX_TABLE_OFFSET |