Booting Linux Kernel using U-Boot
This guide provides instructions for loading Linux Kernel from SD card using Das U-Boot (Universal Bootloader)
Table of Contents
- 1) U-Boot
- 2) Booting Linux Kernel
- 3) Booting Linux using U-Boot
U-Boot allows loading Linux Kernel from different file systems like FAT32, EXT4 etc… This allows us to place the kernel image and RFS (Root File System) on to SD card and eMMC for booting.
1.1) Building and Flashing U-Boot
The native U-Boot support for HiKey doesn’t directly allows to fetch kernel and device tree blob from any storage medium, it needs a bit of work to be done on the U-Boot command line.
First, Build and Flash U-Boot onto HiKey from below tree using the instructions provided in the README.
U-Boot Tree: https://github.com/Mani-Sadhasivam/u-boot Branch: hikey_mmc_fix
2) Booting Linux Kernel
Following instructions provides information about booting Linux kernel along with Debian distro from U-Boot.
2.1) Preparing uImage
Linux kernel needs to be complied and placed onto the SD card in order to allow U-Boot to load it. For compiling Linux kernel, refer this guide. After compilation, generate U-Boot compatible Linux Image using
$ sudo apt-get install u-boot-tools $ mkimage -A arm64 -O linux -C none -T kernel -a 0x00080000 -e 0x00080000 -n HiKey -d arch/arm64/boot/Image uImage
Note: arch/arm64/boot/Image is inside the kernel directory
Once the image has been created successfully, you should get something similar to following output
Image Name: HiKey Created: Thu Dec 20 19:05:49 2018 Image Type: AArch64 Linux Kernel Image (uncompressed) Data Size: 20699648 Bytes = 20214.50 kB = 19.74 MB Load Address: 00080000 Entry Point: 00080000
Now, copy the generated uImage and hi6220-hikey.dtb to FAT32 partition in SD card.
$ sudo cp uImage /path/to/sd $ sudo cp arch/arm64/boot/dts/hisilicon/hi6220-hikey.dtb /path/to/sd
Note: Replace /path/to/sd with the path of SD card’s FAT32 partition.
2.2) Flashing Debian Root File System
Now, flash the pre built Debian Root File System onto the eMMC as per Installation Guide.
Note: By default, Root File System will be flashed into 9th partition of eMMC
3) Booting Linux using U-Boot
Now, insert the SD card onto HiKey and power on the board. By default, boot will stop at the U-Boot prompt. From there, enter below commands to boot Linux Kernel with Debian Root File System.
=> setenv bootargs 'console=ttyAMA3,115200 root=/dev/mmcblk0p9' => load mmc 1:1 $kernel_addr_r uImage => load mmc 1:1 $fdt_addr_r hi6220-hikey.dtb => bootm $kernel_addr_r - $fdt_addr_r
The above commands will fetch uImage and DTB from SD card and loads onto RAM. Finally, it boots Linux kernel with console and root information passed via