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diff --git a/doc/README.nand-boot-ppc440 b/doc/README.nand-boot-ppc440 new file mode 100644 index 0000000..a82a10e --- /dev/null +++ b/doc/README.nand-boot-ppc440 @@ -0,0 +1,36 @@ +----------------------------- +NAND boot on PPC440 platforms +----------------------------- + +This document describes the U-Boot NAND boot feature as it +is implemented for the AMCC Sequoia (PPC440EPx) board. + +The PPC440EP(x)/GR(x) cpu's can boot directly from NAND FLASH, +completely without NOR FLASH. This can be done by using the NAND +boot feature of the 440 NAND flash controller (NDFC). + +Here a short desciption of the different boot stages: + +a) IPL (Initial Program Loader, integrated inside CPU) +------------------------------------------------------ +Will load first 4k from NAND (SPL) into cache and execute it from there. + +b) SPL (Secondary Program Loader) +--------------------------------- +Will load special U-Boot version (NUB) from NAND and execute it. This SPL +has to fit into 4kByte. It sets up the CPU and configures the SDRAM +controller and the NAND controller so that the special U-Boot image can be +loaded from NAND to SDRAM. +This special image is build in the directory "nand_spl". + +c) NUB (NAND U-Boot) +-------------------- +This NAND U-Boot (NUB) is a special U-Boot version which can be started +from RAM. Therefore it mustn't (re-)configure the SDRAM controller. + +On 440EPx the SPL is copied to internal SRAM before the NAND controller +is set up. While still running from cache, I experienced problems accessing +the NAND controller. + + +September 07 2006, Stefan Roese <sr@denx.de> |