Fix for failing to boot from emmc

[grixm]

Due to the shortage of memory chips these days, Radxa is using different emmc models in their boards. For example, I recently ordered a big batch of Rock S0 boards, but they had to be delivered with Sandisk iNAND 32GB emmc drives instead of the typical 8GB option.

The problem is that Armbian did not reliably boot on these new boards. It randomly gets stuck during initialization with the onboard LED endlessly blinking. Some boards works, some did not, some only works sometimes.

 

Long story short, in case other people also have this problem: I found the solution. I believe it is caused by Armbian's Rock S0 device tree enabling the HS200 high speed mode for the emmc device.  (source)
I guess not all emmc chips reliably support this. To fix it, I had to remove the line in the device tree linked in the source above. Actually this should probably be done with a proper device tree modification, but in my case, just to test, I modified the boot scripts. In /boot/boot.cmd, add these lines near the bottom, but ABOVE the "booti ..." line:
 

fdt rm /mmc@ff490000 mmc-hs200-1_8v
fdt set /mmc@ff490000 max-frequency <0x02faf080>

Then recompile in terminal with:
 

mkimage -C none -A arm -T script -d /boot/boot.cmd /boot/boot.scr

 

If you update the kernel/armbian distro these script will probably get overwritten, hence why it should preferably done with a custom device tree instead. But in my case I have frozen updates, and either way this will serve as a starting point for others having the same issue.

Actually, I cannot see this troublesome patch on the 6.18 distro source, so maybe this is old news and no longer a problem on modern images anyway. But my image is still on 6.12, so I figured I'd share anyway. 

Edited 1 hour ago by grixm