[meta-xilinx] Minized support

[Mike Looijmans]

On 22-01-19 16:21, Philip Balister wrote:
> I'm looking at changing the kernel to a fitImge and building a ramdisk
> image for qspi. I'd like to boot from qspi, format the emmc and untar a
> file system (from usb) into the emmc. Finally boot from a kernel on the
> emmc. Does this sound worth upstreaming to meta-xilinx-contrib, or shold
> I just carry it locally?

99% of all our projects boot and run everything from QSPI.

Just put the bootloader, kernel, devicetree into partitions, and create a 
squashfs root filesystem and write it to a QSPI partition as well. You can 
just pass the mtd device as rootfs to the kernel and it'll happily boot with that.

Don't put a ramdisk in QSPI, that's just wasting memory and time. A filesystem 
mounted from QSPI flash will just copy things "on demand" into RAM, so it's 
equally fast to access but since it doesn't have to read the whole filesystem 
into RAM at boot, it's much much faster to boot, and if the pressure goes up, 
it can swap out stuff it no longer needs.

If you want a writable root, just use UBIFS instead of squash. You can even 
put kernel and DT into UBI volumes or files and have u-boot fetch them there.