U-Boot on SPI flash - discussion

[Arwen]

We already have that, nothing to be added. Any bootable SD card installed during power on / reset will cause the eMMC U-Boot to transfer booting to the SD card. That was an update to U-Boot a few weeks ago. We would then use the SD card's OS to fix the U-Boot of the eMMC.

Not if the SPI is first in the boot order...
...

Actually yes. It's the payload of U-Boot installed on the SPI that would do the search for bootable SD card. That's exactly what we have for U-Boot on eMMC now.

When the Pinebook Pros first came, people could not boot off SD cards, if their eMMC had a valid boot loader. One of the first updates to the eMMC load included a U-Boot update that checked for a bootable SD card, BEFORE booting the eMMC. The same can apply to the SPI U-Boot loader.

The SPI U-Boot preferences should probably be;
 - SD card
 - NVMe SSD
 - eMMC

And eventually USB after SD cards but before NVMe SSDs or eMMC.