Since several months I have used my Nanopi R5S in dual boot mode, on the MMC there is FriendlyWRT and on the SD there is Dietpi. Without the SD card it boots from MMC, with the SD it boots from SD, all fine.
Since a while (several months) I did not do an update, so I did now. It asked me to have a special R5S kernel flashed so I did. Since this moment, it does not boot from SD card but always from MMC.
So no problem, just download the latest DietPi image, flash it with Balena Etcher, still boots from MMC.
Using different SD cards (all worked before) flashing the DietPi Image, still boots from MMC.
Using different power supplies (all worked before), still boots from MMC.
Here Nanopi R5C seems to ignore SD Card in boot order the solution is to kill the MMC which is not an option for me. I do need to keep the MMC as it is.
So I have read about u-boot and tried to enter it. I did attach the R5S to a screen via HDMI and connected a USB keyboard but it did not enter u-boot regardless which key (enter, ESC) I pressed. What did I do wrong and how do I change the boot order?
Is there any way I could boot from MMC and then (with the OS running from MMC) edit the config? Is there a uboot textfile I could edit?
UPDATE: On my local machine I have found a stone-age image of Dietpi from 03/2023 so 18 months old, flashed it to the card - starts like a charm. Updates and this time I opted NOT to use the new kernel - now it restarts straight away!
=> it seems like there is some issue with the new kernel that prevents it from acting as boot device. Is there anything I can do to facilitate bugfixing?