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diff --git a/roms/u-boot/doc/README.atmel_pmecc b/roms/u-boot/doc/README.atmel_pmecc new file mode 100644 index 000000000..c86d08577 --- /dev/null +++ b/roms/u-boot/doc/README.atmel_pmecc @@ -0,0 +1,49 @@ +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. + +Take 'configs/at91sam9x5ek_nandflash_defconfig' as an example, the board +configuration file has the following entries: + + CONFIG_PMECC_CAP=2 + CONFIG_PMECC_SECTOR_SIZE=512 + CONFIG_SPL_GENERATE_ATMEL_PMECC_HEADER=y + +How to enable PMECC header for direct programmable boot.bin +----------------------------------------------------------- +2014-05-19 Andreas Bießmann <andreas@biessmann.org> + +The usual way to program SPL into NAND flash is to use the SAM-BA Atmel tool. +This however is often not usable when doing field updates. To be able to +program a SPL binary into NAND flash we need to add the PMECC header to the +binary before. Chapter '12.4.4.1 NAND Flash Boot: NAND Flash Detection' in +sama5d3 SoC spec (as of 03. April 2014) defines how this PMECC header has to +look like. In order to do so we have a new image type added to mkimage to +generate this PMECC header and integrated this into the build process of SPL. + +To enable the generation of atmel PMECC header for SPL one needs to define +CONFIG_SPL_GENERATE_ATMEL_PMECC_HEADER. The required parameters are taken from +board configuration and compiled into the host tools atmel_pmecc_params. This +tool will be called in build process to parametrize mkimage for atmelimage +type. The mkimage tool has intentionally _not_ compiled in those parameters. + +The mkimage image type atmelimage also set the 6'th interrupt vector to the +correct value. This feature can also be used to setup a boot.bin for MMC boot. |