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Then, convert the generated Kernel image to the format recognized by U-Boot(uImage) using mkimage tool.īootargs=root=/dev/mmcblk1p1 rw rootwait console=tty0 console=ttyMSM0,115200n8 rootfs=ext4 noinitrd selinux=0īootcmd=ext4load mmc 1:1 $Ībove environment variables instructs U-Boot to fetch Kernel image and device tree blob from /boot/ directory in SD card’s first partition. Now, build the Linux Kernel along with device tree using the instructions available in release notes. By the end of this step, the first partition of SD card should have entire Root File System populated. #Linux u boot tutorial download#But, we are going to place the Kernel image under RFS itself.Īfter formatting SD card, download the OpenEmbedded RFS from 96Boards build, extract it and flash onto SD card’s first partition. This is the place, we will store the RFS (Root File System), Kernel image, dtb, uEnv.txt etc… Usually Kenrel image would be placed in FAT partition and RFS would be in ext4 partition. The complete guide containing the instructions is avaialbe in 96Boards Documentation repository.įirst, SD card needs to be formatted in such as way that the first partition should be of ext4 type. Now, lets get into the detail of booting Linux from SD card using U-Boot. Below, is the booting process involved in Dragonboard410c for U-Boot: In those cases, SPL will initialize some externally connected peripherals like eMMC,SRAM etc., and then it loads the final U-Boot onto external SRAM.īut for Dragonboard, SPL is not needed as the U-Boot finds its place in third stage of the booting process and by the time ample amount of external RAM and Flash is available for it to use. It is often used in cases where the memory available for second stage bootloader is scarce or the second stage bootloader has to boot using internal RAM/Flash. #Linux u boot tutorial full#SPL is the stripped version of the full fledged U-Boot binary. U-Boot binary is available in two flavours: The reason behind that is, in most of the SoC’s there will a ROM bootloader which gets executed first. Usually U-Boot will be put up as a secondary or later stage bootloader for the SBC’s. It offers wide range of flexibility in terms of booting from different sources and so on. U-Bootĭas U-Boot (Universal Bootloader) is the the popular Open source bootloader for Embedded devices. #Linux u boot tutorial how to#This blog addresses this pitfall and also explains about how to boot Linux from SD card using the environment from U-Boot’s uEnv.txt. One of which is extracting boot environment from uEnv.txt. Even though U-Boot is supported for couple of our 96Boards, we are still lagging behind using the nice to have features of it. This file will need to be placed in the first partition of the bootable SD card.Often I hear from people that it’d be nice to have U-Boot running on 96Boards at full pace. Now that we have a compiler that will correctly compile U-Boot, we will configure and compile the source. So we will download version 6.4 of the gcc compiler to build U-Boot cd Unfortunately, the source in this tag does not compile with the 7.x version of the gcc compiler. We are going to use the following tag: git checkout rel_socfpga_v2013.01.01_18.06.02_pr Compiling U-BOOT We can look at the released BSPs by using the following command: git tag -l rel_socfpga* Once inside the u-boot-socfpga directory, we need to check out a recent BSP release. We can grab a copy of the Intel U-Boot source from GitHub. #Linux u boot tutorial code#Instead, we are simply going to download U-Boot from the public Intel GIT repository and compile the source code into a U-Boot image. Downloading U-Bootįor the purposes of our class, we will not delve into the specifics of what U-Boot does or how to develop a board support package (BSP) for the Intel SoC. U-Boot is responsible for initializing enough of the hardware so that the Linux kernel can be loaded into memory and begin its boot process. As important as all of these tasks may be, the primary job of U-Boot is preparing the hardware to boot into Linux. ![]() These tests can include detecting devices on the PCIe bus, memory tests, and initializing board specific data. ![]() ![]() U-Boot is commonly used to run diagnostic tests on an embedded system. U-Boot is the ubiquitous boot loader for most non-x86 based CPUs. ![]()
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