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How to enable PMECC(Programmable Multibit ECC) for nand on Atmel SoCs
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2012-08-22 Josh Wu <josh.wu@atmel.com>
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The Programmable Multibit ECC (PMECC) controller is a programmable binary
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BCH(Bose, Chaudhuri and Hocquenghem) encoder and decoder. This controller
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can be used to support both SLC and MLC NAND Flash devices. It supports to
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generate ECC to correct 2, 4, 8, 12 or 24 bits of error per sector (512 or
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1024 bytes) of data.
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Following Atmel AT91 products support PMECC.
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- AT91SAM9X25, X35, G25, G15, G35 (tested)
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- AT91SAM9N12 (not tested, Should work)
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As soon as your nand flash software ECC works, you can enable PMECC.
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To use PMECC in this driver, the user needs to set:
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1. the PMECC correction error bits capability: CONFIG_PMECC_CAP.
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It can be 2, 4, 8, 12 or 24.
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2. The PMECC sector size: CONFIG_PMECC_SECTOR_SIZE.
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It only can be 512 or 1024.
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Take AT91SAM9X5EK as an example, the board definition file likes:
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/* PMECC & PMERRLOC */
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#define CONFIG_ATMEL_NAND_HWECC 1
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#define CONFIG_ATMEL_NAND_HW_PMECC 1
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#define CONFIG_PMECC_CAP 2
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#define CONFIG_PMECC_SECTOR_SIZE 512
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How to enable PMECC header for direct programmable boot.bin
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2014-05-19 Andreas Bießmann <andreas@biessmann.org>
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The usual way to program SPL into NAND flash is to use the SAM-BA Atmel tool.
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This however is often not usable when doing field updates. To be able to
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program a SPL binary into NAND flash we need to add the PMECC header to the
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binary before. Chapter '12.4.4.1 NAND Flash Boot: NAND Flash Detection' in
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sama5d3 SoC spec (as of 03. April 2014) defines how this PMECC header has to
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look like. In order to do so we have a new image type added to mkimage to
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generate this PMECC header and integrated this into the build process of SPL.
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To enable the generation of atmel PMECC header for SPL one need to define
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CONFIG_SPL_GENERATE_ATMEL_PMECC_HEADER. The required parameters are taken from
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board configuration and compiled into the host tools atmel_pmecc_params. This
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tool will be called in build process to parametrize mkimage for atmelimage
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type. The mkimage tool has intentionally _not_ compiled in those parameters.
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The mkimage image type atmelimage also set the 6'th interrupt vector to the
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correct value. This feature can also be used to setup a boot.bin for MMC boot.
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