Linux u boot12/29/2023 onchip ROM of the ARM CPU) from a supported boot device, such as an SD card, SATA drive, NOR flash (e.g. U-Boot is both a first-stage and second-stage bootloader. Loading Device Tree to 8ffd9000, end 8ffed310. Loading Device Tree to 8ffee000, end 8ffff310. Image Type: ARM Linux Kernel Image (uncompressed) # Booting kernel from Legacy Image at 82000000. => setenv args_mmc 'setenv bootargs console=$ Kernel offset location is defined in the sources by the following config : CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR 0x900Įnvironment offset location and size are defined by the following configs: #define CONFIG_ENV_OFFSET 0x0e0000 U-boot offset location is defined in the sources by the following config : CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR 0x300 We are going to use u-boot v2017.05-rc3: $ git clone git:///u-boot.git This address is hard coded in the Boot ROM and specific to processor. SPL* offset is the address from which the Boot ROM can fetch bootloader. As result the boot is even faster ! Partition # If Boot Rom Code support it, we recommend to store and boot the SPL from raw partition and by this mean also u-Boot and Linux Kernel to skip the overhead of using a Filesystem. Nevertheless the procedure should be almost identical to other ARM based boards supporting the SPL framework. We will use a Beaglebone Black as hardware example to showcase the setup, booting either from an eMMC or SD Card. Third stage – u-Bootĭas u-Boot aims to offer a flexibel way to load and start the Linux Kernel from a different type of devices, it also provides rich features for a bootloader, such as a command line interface, Shell Scripting, Support of a variety of Filesystems, networking and other options that are very helpful during initial Hardware Bring-Up and development process, but can be bypassed for the production by enabling the Falcon-Mode and save by the way some precious seconds of the boot time !įalcon Mode Configure and enable Falcon-Mode So when u-Boot is built for a platform that requires SPL, it generate two binaries : SPL (MLO file) and u-Boot image. ![]() It shares the same u-Boot’s sources but with a minimal set of code. To handle this limitation, u-Boot adopted the SPL (Secondary Program Loader) approach which consists of creating a very small pre-loader that after configuring and initializing peripherals and the main system memory can load the full blown u-Boot. ![]() Second stage – SPLĪ typical u-Boot image is around few hundreds KB size (~300KB) which does not fit inside internal SRAM of most ARM processor. The main goal here is to perform basic peripherals initialization such as PLLs, system clocks setup then find a boot device from which load a bootloader such as u-Boot. In case of a Secure Boot processor it will also verify the code authenticity before its execution.Īt this stage, Boot ROM code is not aware about memory type and different interconnected peripherals. It contains the very first code which is executed on power-on or reset.ĭepending on the configuration of the bootstrap pins or internal fuses it may decide from which media to load and run the next piece of software. This is the primary program loader residing on a read-only flash memory (ROM) integrated directly into the processor chip.
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