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Diffstat (limited to 'qemu/roms/u-boot/doc/README.ramboot-ppc85xx')
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diff --git a/qemu/roms/u-boot/doc/README.ramboot-ppc85xx b/qemu/roms/u-boot/doc/README.ramboot-ppc85xx deleted file mode 100644 index 5cc546a36..000000000 --- a/qemu/roms/u-boot/doc/README.ramboot-ppc85xx +++ /dev/null @@ -1,102 +0,0 @@ - RAMBOOT for MPC85xx Platforms - ============================== - -RAMBOOT literally means boot from DDR. But since DDR is volatile memory some -pre-mechanism is required to load the DDR with the bootloader binary. -- In case of SD and SPI boot this is done by BootROM code inside the chip - itself. -- In case of NAND boot FCM supports loading initial 4K code from NAND flash - which can initialize the DDR and get the complete bootloader copied to DDR. - -In addition to the above there could be some more methods to initialize the DDR -and load it manually. -Two of them are described below.There is also an explanation as to where these -methods could be handy. -1. Load the RAM based bootloader onto DDR via JTAG/BDI interface. And then - execute the bootloader from DDR. - This may be handy in the following cases: - - In very early stage of platform bringup where other boot options are not - functional because of various reasons. - - In case the support to program the flashes on the board is not available. - -2. Load the RAM based bootloader onto DDR using already existing bootloader on - the board.And then execute the bootloader from DDR. - Some usecases where this may be used: - - While developing some new feature of u-boot, for example USB driver or - SPI driver. - Suppose the board already has a working bootloader on it. And you would - prefer to keep it intact, at the same time want to test your bootloader. - In this case you can get your test bootloader binary into DDR via tftp - for example. Then execute the test bootloader. - - Suppose a platform already has a propreitery bootloader which does not - support for example AMP boot. In this case also RAM boot loader can be - utilized. - - So basically when the original bootloader is required to be kept intact - RAM based bootloader can offer an updated bootloader on the system. - -Both the above Bootloaders are slight variants of SDcard or SPI Flash -bootloader or for that matter even NAND bootloader. -All of them define CONFIG_SYS_RAMBOOT. -The main difference among all of them is the way the pre-environment is getting -configured and who is doing that. -- In case of SD card and SPI flash bootloader this is done by On Chip BootROM inside the Si itself. -- In case of NAND boot SPL/TPL code does it with some support from Si itself. -- In case of the pure RAM based bootloaders we have to do it by JTAG manually or already existing bootloader. - -How to use them: -1. Using JTAG - Boot up in core hold off mode or stop the core after reset using JTAG - interface. - Preconfigure DDR/L2SRAM through JTAG interface. - - setup DDR controller registers. - - setup DDR LAWs - - setup DDR TLB - Load the RAM based boot loader to the proper location in DDR/L2SRAM. - set up IAR (Instruction counter properly) - Enable the core to execute. - -2. Using already existing bootloader. - get the rambased boot loader binary into DDR/L2SRAM via tftp. - execute the RAM based bootloader. - => tftp 11000000 u-boot-ram.bin - => go 1107f000 - -Please note that L2SRAM can also be used instead of DDR if the SOC has -sufficient size of L2SRAM. - -Necessary Code changes Required: -===================================== -Please note that below mentioned changes are for 85xx platforms. -They have been tested on P1020/P2020/P1010 RDB. - -The main difference between the above two methods from technical perspective is -that in 1st case SOC is just out of reset so it is in default configuration. -(CCSRBAR is at 0xff700000). -In the 2nd case bootloader has already re-located CCSRBAR to 0xffe00000 - -1. File name-> boards.cfg - There can be added specific Make options for RAMBoot. We can keep different - options for the two cases mentioned above. - for example - P1020RDB_JTAG_RAMBOOT and P1020RDB_GO_RAMBOOT. - -2. platform config file - for example include/configs/P1_P2_RDB.h - - #ifdef CONFIG_RAMBOOT - #define CONFIG_SDCARD - #endif - - This will finally use the CONFIG_SYS_RAMBOOT. - -3. File name-> arch/powerpc/include/asm/config_mpc85xx.h - In the section of the particular SOC, for example P1020, - - #if defined(CONFIG_GO) - #define CONFIG_SYS_CCSRBAR_DEFAULT 0xffe00000 - #else - #define CONFIG_SYS_CCSRBAR_DEFAULT 0xff700000 - #endif - -For JTAG RAMBOOT this is not required because CCSRBAR is at ff700000. |