| 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 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 |
| |
| 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 need 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. |
