[U-Boot] Download kernel/rootfs and boot on them

[Shanx]

Hi,

We are working with a few cards. We generate linux embedded images with
Yocto (using U-boot as bootloader), and we deploy it manually on SD cards.
This works well for now, when we are in test phase and don't have a lot of
cards. But later, it'll be definitely too slow.

We have a central server for the network of the cards. Currently, this is a
simple DHCP server, affecting IP addresses depending on the MAC addresses
of the cards. First, we have thought to make a PXE server, but it seems
that the i.MX6 internal boot ROM loader does not support the PXE boot
process.

So we try to load only u-boot on the cards, and then use a script (a
boot.scr) to download all that is needed (zImage, dtb and rootfs) to boot.
We don’t want to use NFS (no thin client, we want all the necessary to be
downloaded on the cards). Currently, we can download the kernel and the dtb
file using this:


U-Boot > dhcp ${image}; tftpboot ${fdt_addr} ${fdt_file} ; fdt addr
${fdt_addr}

U-Boot > bootz ${loadaddr} - ${fdt_addr}


Of course, as there isn’t any rootfs, the booting of the kernel ends with a
kernel panic. But we don’t know how to download the rootfs and make the
kernel using it. Any suggestion how to do it is welcome. Thanks.