Following on from where we left off, now let’s actually use FEL for the whole process, not just to get uboot loaded. In the last piece, once uboot was loaded, we used uboot+tftp to boot our openwrt ramdisk, but FEL can do it all in one hit, over usb, according to http://linux-sunxi.org/FEL/USBBoot#Booting_the_whole_system_over_USB_.28U-Boot_.2B_kernel_.2B_initramfs.29 and that’s way more useful on things that might not have an ethernet port onboard.
We basically just take our steps from the last one, and add them as options to the sunxi-fel tool.
First, we trim down our “my.env” file, as now it just needs to boot.
$ cat my-fel.cmd
setenv bootargs console=ttyS0,115200 earlyprintk
bootm $kernel_addr_r - $fdt_addr_r
Now, we convert that to the “scr” file that uboot will run magically.
$ tools/mkimage -C none -A arm -T script -d my-fel.cmd my-fel.scr
Now, use sunxi-fel with all the wonderful paths into the build guts of openwrt.
$ sunxi-fel uboot u-boot-sunxi-with-spl.bin write-with-progress 0x42000000 /home/karlp/src/openwrt-git/bin/targets/sunxi/cortexa7/openwrt-sunxi-cortexa7-sun8i-h3-nanopi-neo-initramfs-kernel.bin write 0x43000000 ~/src/openwrt-git/build_dir/target-arm_cortex-a7+neon-vfpv4_musl_eabi/linux-sunxi_cortexa7/linux-4.14.82/arch/arm/boot/dts/sun8i-h3-nanopi-neo.dtb write 0x43100000 my-fel.scr
100% [================================================] 4013 kB, 770.4 kB/s
Because openwrt’s buildroot builds us a nice kernel+ramdisk image out of the box, (well, if you select “ramdisk” in the image settings) we don’t need to write the uImage and rootfs separately as indicated on the http://linux-sunxi.org/FEL/USBBoot page.
For reference, the openwrt diffconfig to build this is just
$ ./scripts/diffconfig.sh
CONFIG_TARGET_sunxi=y
CONFIG_TARGET_sunxi_cortexa7=y
CONFIG_TARGET_sunxi_cortexa7_DEVICE_sun8i-h3-nanopi-neo=y
CONFIG_DEVEL=y
CONFIG_TARGET_INITRAMFS_COMPRESSION_NONE=y
CONFIG_TARGET_ROOTFS_INITRAMFS=y
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