U-Boot on SPI flash - discussion

[zaius]

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.

Right, so SD is first in the boot order.  Unless I'm misunderstanding something, currently, the ROM goes to SPI, doesn't find boot, then goes to eMMC, which has boot, but tells it to boot from SD first.   So if the SPI has boot, then it should tell to it  to boot from SD first (which is what we have on the eMMC now.)  If it doesn't find a bootable SD, it would proceed to boot from SPI or eMMC, respectively.

Therefore, we agree having an SPI boot requires the SPI to look for a bootable SD to have that same recovery procedure.  So moving forward, since disabling or overriding the SPI is difficult, the SPI writing procedure should also "read after write" to make sure it was written correctly.