| Booting U-Boot on a MXS processor | |
| ================================= | |
| This document describes the MXS U-Boot port. This document mostly covers topics | |
| related to making the module/board bootable. | |
| Terminology | |
| ----------- | |
| The term "MXS" refers to a family of Freescale SoCs that is composed by MX23 | |
| and MX28. | |
| 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 MXS based board | |
| 3) Installation of U-Boot for a MXS based board to SD card | |
| 4) Installation of U-Boot into NAND flash on a MX28 based board | |
| 5) Installation of U-Boot into SPI NOR flash on a MX28 based board | |
| 1) Prerequisites | |
| ---------------- | |
| To make a MXS based board bootable, some tools are necessary. The only | |
| mandatory tool is the "mxsboot" tool found in U-Boot source tree. The | |
| tool is built automatically when compiling U-Boot for i.MX23 or i.MX28. | |
| The production of BootStream image is handled via "mkimage", which is | |
| also part of the U-Boot source tree. The "mkimage" requires OpenSSL | |
| development libraries to be installed. In case of Debian and derivates, | |
| this is installed by running: | |
| $ sudo apt-get install libssl-dev | |
| NOTE: The "elftosb" tool distributed by Freescale Semiconductor is no | |
| longer necessary for general use of U-Boot on i.MX23 and i.MX28. | |
| The mkimage supports generation of BootStream images encrypted | |
| with a zero key, which is the vast majority of use-cases. In | |
| case you do need to produce image encrypted with non-zero key | |
| or other special features, please use the "elftosb" tool, | |
| otherwise continue to section 2). The installation procedure of | |
| the "elftosb" is outlined below: | |
| 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 MXS based board | |
| ------------------------------------------- | |
| Compiling the U-Boot for a MXS 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 MXS based board | |
| $ make <mxs_based_board_name>_config | |
| Examples: | |
| 1. For building U-Boot for Aries M28EVK board: | |
| $ make m28evk_config | |
| 2. For building U-Boot for Freescale MX28EVK board: | |
| $ make mx28evk_config | |
| 3. For building U-Boot for Freescale MX23EVK board: | |
| $ make mx23evk_config | |
| 4. For building U-Boot for Olimex MX23 Olinuxino board: | |
| $ make mx23_olinuxino_config | |
| Lastly, compile U-Boot and prepare a "BootStream". The "BootStream" is a special | |
| type of file, which MXS CPUs 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. | |
| NOTE: The process that produces u-boot.sb uses the mkimage to generate the | |
| BootStream. The BootStream is encrypted with zero key. In case you need | |
| some special features of the BootStream and plan on using the "elftosb" | |
| tool instead, the invocation to produce a compatible BootStream with the | |
| one produced by mkimage is outlined below. For further details, refer to | |
| the documentation bundled with the "elftosb" package. | |
| $ elftosb -zf imx23 -c arch/arm/cpu/arm926ejs/mxs/u-boot-imx23.bd \ | |
| -o u-boot.sb | |
| $ elftosb -zf imx28 -c arch/arm/cpu/arm926ejs/mxs/u-boot-imx28.bd \ | |
| -o u-boot.sb | |
| 3) Installation of U-Boot for a MXS based board to SD card | |
| ---------------------------------------------------------- | |
| To boot a MXS based board from SD, set the boot mode DIP switches according to | |
| to MX28 manual, section 12.2.1 (Table 12-2) or MX23 manual, section 35.1.2 | |
| (Table 35-3). | |
| The SD card used 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 the MXS 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 on a MX28 based board | |
| --------------------------------------------------------------- | |
| To boot a MX28 based board from NAND, set the boot mode DIP switches according | |
| to MX28 manual section 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" variable. | |
| 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" variable. | |
| 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 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. | |
| 5) Installation of U-Boot into SPI NOR flash on a MX28 based board | |
| ------------------------------------------------------------------ | |
| The u-boot.sb file can be directly written to SPI NOR from U-Boot prompt. | |
| Load u-boot.sb into RAM, this can be done in several ways and one way is to use | |
| tftp: | |
| => tftp u-boot.sb 0x42000000 | |
| Probe the SPI NOR flash: | |
| => sf probe | |
| (SPI NOR should be succesfully detected in this step) | |
| Erase the blocks where U-Boot binary will be written to: | |
| => sf erase 0x0 0x80000 | |
| Write u-boot.sb to SPI NOR: | |
| => sf write 0x42000000 0 0x80000 | |
| Power off the board and set the boot mode DIP switches to boot from the SPI NOR | |
| according to MX28 manual section 12.2.1 (Table 12-2) | |
| Last step is to power up the board and U-Boot should start from SPI NOR. |