| Booting U-boot on a MX28 processor | |
| ================================== | |
| This document describes the MX28 U-Boot port. This document mostly | |
| covers topics related to making the module/board bootable. | |
| Terminology | |
| ----------- | |
| The dollar symbol ($) introduces a snipped of shell code. This shall be typed | |
| into the unix command prompt in U-Boot source code root directory. | |
| The (=>) introduces a snipped of code that should by typed into U-Boot command | |
| prompt | |
| Contents | |
| -------- | |
| 1) Prerequisites | |
| 2) Compiling U-Boot for a MX28 based board | |
| 3) Installation of U-Boot for a MX28 based board to SD card | |
| 4) Installation of U-Boot into NAND flash | |
| 1) Prerequisites | |
| ---------------- | |
| To make a MX28 based board bootable, some tools are necessary. The first one | |
| is the "elftosb" tool distributed by Freescale Semiconductor. The other one | |
| is the "mxsboot" tool found in U-Boot source tree. | |
| Firstly, obtain the elftosb archive from the following location: | |
| ftp://ftp.denx.de/pub/tools/elftosb-10.12.01.tar.gz | |
| We use a $VER variable here to denote the current version. At the time of | |
| writing of this document, that is "10.12.01". To obtain the file from command | |
| line, use: | |
| $ VER="10.12.01" | |
| $ wget ftp://ftp.denx.de/pub/tools/elftosb-${VER}.tar.gz | |
| Extract the file: | |
| $ tar xzf elftosb-${VER}.tar.gz | |
| Compile the file. We need to manually tell the linker to use also libm: | |
| $ cd elftosb-${VER}/ | |
| $ make LIBS="-lstdc++ -lm" elftosb | |
| Optionally, remove debugging symbols from elftosb: | |
| $ strip bld/linux/elftosb | |
| Finally, install the "elftosb" binary. The "install" target is missing, so just | |
| copy the binary by hand: | |
| $ sudo cp bld/linux/elftosb /usr/local/bin/ | |
| Make sure the "elftosb" binary can be found in your $PATH, in this case this | |
| means "/usr/local/bin/" has to be in your $PATH. | |
| 2) Compiling U-Boot for a MX28 based board | |
| ------------------------------------------- | |
| Compiling the U-Boot for a MX28 board is straightforward and done as compiling U-Boot | |
| for any other ARM device. For cross-compiler setup, please refer to ELDK5.0 | |
| documentation. First, clean up the source code: | |
| $ make mrproper | |
| Next, configure U-Boot for a MX28 based board | |
| $ make <mx28_based_board_name>_config | |
| Examples: | |
| 1. For building U-boot for Denx M28EVK board: | |
| $ make m28evk_config | |
| 2. For building U-boot for Freescale MX28EVK board: | |
| $ make mx28evk_config | |
| Lastly, compile U-Boot and prepare a "BootStream". The "BootStream" is a special | |
| type of file, which the i.MX28 CPU can boot. This is handled by the following | |
| command: | |
| $ make u-boot.sb | |
| HINT: To speed-up the build process, you can add -j<N>, where N is number of | |
| compiler instances that'll run in parallel. | |
| The code produces "u-boot.sb" file. This file needs to be augmented with a | |
| proper header to allow successful boot from SD or NAND. Adding the header is | |
| discussed in the following chapters. | |
| 3) Installation of U-Boot for a MX28 based board to SD card | |
| ----------------------------------------------------------- | |
| To boot a MX28 based board from SD, set the boot mode DIP switches according | |
| to i.MX28 manual chapter 12.2.1 (Table 12-2), PORT=SSP0, SD/MMC master on | |
| SSP0, 3.3V. | |
| An SD card the i.MX28 CPU can use to boot U-Boot must contain a DOS partition | |
| table, which in turn carries a partition of special type and which contains a | |
| special header. The rest of partitions in the DOS partition table can be used | |
| by the user. | |
| To prepare such partition, use your favourite partitioning tool. The partition | |
| must have the following parameters: | |
| * Start sector .......... sector 2048 | |
| * Partition size ........ at least 1024 kb | |
| * Partition type ........ 0x53 (sometimes "OnTrack DM6 Aux3") | |
| For example in Linux fdisk, the sequence for a clear card follows. Be sure to | |
| run fdisk with the option "-u=sectors" to set units to sectors: | |
| * o ..................... create a clear partition table | |
| * n ..................... create new partition | |
| * p ............. primary partition | |
| * 1 ............. first partition | |
| * 2048 .......... first sector is 2048 | |
| * +1M ........... make the partition 1Mb big | |
| * t 1 ................... change first partition ID | |
| * 53 ............ change the ID to 0x53 (OnTrack DM6 Aux3) | |
| * <create other partitions> | |
| * w ..................... write partition table to disk | |
| The partition layout is ready, next the special partition must be filled with | |
| proper contents. The contents is generated by running the following command | |
| (see chapter 2)): | |
| $ ./tools/mxsboot sd u-boot.sb u-boot.sd | |
| The resulting file, "u-boot.sd", shall then be written to the partition. In this | |
| case, we assume the first partition of the SD card is /dev/mmcblk0p1: | |
| $ dd if=u-boot.sd of=/dev/mmcblk0p1 | |
| Last step is to insert the card into MX28 based board and boot. | |
| NOTE: If the user needs to adjust the start sector, the "mxsboot" tool contains | |
| a "-p" switch for that purpose. The "-p" switch takes the sector number as | |
| an argument. | |
| 4) Installation of U-Boot into NAND flash | |
| ----------------------------------------- | |
| To boot a MX28 based board from NAND, set the boot mode DIP switches according to i.MX28 | |
| manual chapter 12.2.1 (Table 12-2), PORT=GPMI, NAND 1.8 V. | |
| There are two possibilities when preparing an image writable to NAND flash. | |
| I) The NAND wasn't written at all yet or the BCB is broken | |
| ---------------------------------------------------------- | |
| In this case, both BCB (FCB and DBBT) and firmware needs to be | |
| written to NAND. To generate NAND image containing all these, | |
| there is a tool called "mxsboot" in the "tools/" directory. The tool | |
| is invoked on "u-boot.sb" file from chapter 2): | |
| $ ./tools/mxsboot nand u-boot.sb u-boot.nand | |
| NOTE: The above invokation works for NAND flash with geometry of | |
| 2048b per page, 64b OOB data, 128kb erase size. If your chip | |
| has a different geometry, please use: | |
| -w <size> change page size (default 2048 b) | |
| -o <size> change oob size (default 64 b) | |
| -e <size> change erase size (default 131072 b) | |
| The geometry information can be obtained from running U-Boot | |
| on the MX28 board by issuing the "nand info" command. | |
| The resulting file, "u-boot.nand" can be written directly to NAND | |
| from the U-Boot prompt. To simplify the process, the U-Boot default | |
| environment contains script "update_nand_full" to update the system. | |
| This script expects a working TFTP server containing the file | |
| "u-boot.nand" in it's root directory. This can be changed by | |
| adjusting the "update_nand_full_filename" varible. | |
| To update the system, run the following in U-Boot prompt: | |
| => run update_nand_full | |
| In case you would only need to update the bootloader in future, | |
| see II) below. | |
| II) The NAND was already written with a good BCB | |
| ------------------------------------------------ | |
| This part applies after the part I) above was done at least once. | |
| If part I) above was done correctly already, there is no need to | |
| write the FCB and DBBT parts of NAND again. It's possible to upgrade | |
| only the bootloader image. | |
| To simplify the process of firmware update, the U-Boot default | |
| environment contains script "update_nand_firmware" to update only | |
| the firmware, without rewriting FCB and DBBT. | |
| This script expects a working TFTP server containing the file | |
| "u-boot.sb" in it's root directory. This can be changed by | |
| adjusting the "update_nand_firmware_filename" varible. | |
| To update the system, run the following in U-Boot prompt: | |
| => run update_nand_firmware | |
| III) Special settings for the update scripts | |
| -------------------------------------------- | |
| There is a slight possibility of the user wanting to adjust the | |
| STRIDE and COUNT options of the NAND boot. For description of these, | |
| see i.MX28 manual section 12.12.1.2 and 12.12.1.3. | |
| The update scripts take this possibility into account. In case the | |
| user changes STRIDE by blowing fuses, the user also has to change | |
| "update_nand_stride" variable. In case the user changes COUNT by | |
| blowing fuses, the user also has to change "update_nand_count" | |
| variable for the update scripts to work correctly. | |
| In case the user needs to boot a firmware image bigger than 1Mb, the | |
| user has to adjust the "update_nand_firmware_maxsz" variable for the | |
| update scripts to work properly. |