Banana Pi M2 Zero (Allwinner H2+)

CityAceE Yes, of course, I tested the LT version, but unfortunately, the result is also disappointing.

Thanks for testing. I suppose that's another shortcut coming to bite me...

On H616, every board needs its own image, but I assumed that all H3/H2+ boards are similar enough that one bootloader will fit them all. It looks like that isn't the case after all...

I'll see if I can get around to figure this out. If you want to try it yourself, you can clone the basicengine-buildroot and do a make basicengine_h3_defconfig and then change BR2_TARGET_UBOOT_BOARD_DEFCONFIG in .config to bananapi_m2_zero and make and see if that works (image will be in output/images/sdcard.img).

(Looking at my shell history, building basicengine-buildroot needs the following non-obvious packages in addition to all the usual stuff buildroot needs: p7zip ninja-build gettext python3 python3-polib asciidoctor libsdl2-dev libgpiod-dev texi2html texinfo libncurses-dev help2man)

If that works, I'll have to fix the git build script to create multiple H3 images (just like the H616), and we'll have to read through the device trees to see which board has which MMC config...

Either way, thanks for your help.

CityAceE At least in the basicengine_h3_defconfig file (and probably in orangepi_lite_defconfig) in the BR2_LINUX_KERNEL_INTREE_DTS_NAME section, add a link to the sun8i-h2-plus-bananapi-m2-zero tree. And also sun8i-h2-plus-bananapi-m2-zero.dtb to the list in the file board/basicengine/h3/genimage.cfg. You also need to edit the start menu boot.scr and add Banana Pi M2 Zero to it.

I simply assumed I had dumped all the H2+/H3 device trees into the image already. Must have missed that one.
That said, I just checked linux-sunxi.org, and what they say is this:

Despite its name the M2 Zero is totally incompatible to Banana Pi/M1/M1+/Pro/M2/M2U/M3/M64 due to a different SoC - requiring different boot loaders and drivers. It's another attempt to cash-in on the Banana Pi's popularity with a SBC sharing only Brand-name, form factor and GPIO header.

(Thanks to libv for not mincing words here. )

So I don't think I will be engaging with this thing any further when it comes to a bare-metal (RX) implementation.

With LT that is another matter, though. If you are willing to take on the job of bending the basicengine_h3_lt_defconfig into something that works on the BPi M2 Zero, I'd be more than happy to include the result in the repo and the git builds.

CityAceE If you do all this and successfully compile the project, then Banana Pi will boot. We will see the boot log in the console and on the monitor for a short time. Then the monitor will turn off and boot log will continue only to the UART console. The necessary partitions will be created on the SD. However, the BASIC section will not be filled with the necessary data. It all ends with a command line prompt. And you can even log in as root without a password.

That is a bit strange. There is nothing that in any way depends on the flavor (RX or LT), board, CPU or anything hardware-related when it comes to partitioning. Could you perhaps go and edit /etc/init.d/S30part and add set -x in the second line? Then we would be able to see what's going on in that script.

Maybe it's simply the reboot that fails. The sequence is:

• create partition
• create a file named /make_vfat file in the root directory
• reboot
• create FAT32 file system
• remove /make_vfat
• mount FAT32 file system
• extract data

If the reboot fails, you will end up with an SD card with the right partitions, but no file system on the BASIC partition and a /make_vfat file on the root partition. In that case, simply power cycling the board should do the trick.

CityAceE I'm experimenting with the same SD cards. Interestingly, after recreating the file system, the same files that I recorded earlier remain on the BASIC section, for example, video recording files of the process. I have not studied why this happens, but I have noticed this behavior.

That is intentional so you can update to a later version without losing your files. The setup code will only create a new file system if there isn't one already, and it will only unpack the system files if there is no sys directory.

Excellent. Please post the config here so I can add it.

Also, please try to reproduce the hangs without "quiet" in the bootargs so we can see where it happens. (I added that to silence the boot messages because the serial port is slow enough to slow down the boot process noticeably.)

CityAceE Next, the computer cannot be loaded, it freezes every time after clicking on the reset. But if you turn off the computer and then turn it on, then the kernel can boot. If you insert a USB dongle during "freezing", then information will be recorded in the log, and it will also be recorded if you remove the dongle. However, there is still no further loading of the kernel. I've tried recording to different SD cards, but the behavior is always the same. This is repeated whenever there is no "quiet" option. When there is a "quiet", then freezes are not so frequent and halt can be defeated by pressing reset.

If found this post on the Banana Pi forum:
https://forum.banana-pi.org/t/waiting-for-root-mmc-device/16676

So adding

               mmc0 = &mmc0;
               mmc1 = &mmc1;
               mmc2 = &mmc2;

to the aliases block in the device tree is supposed to fix this. And I actually think it would. In the boot log you posted there is this line:

CityAceE [ 3.065243] mmc0: new high speed SDIO card at address 0001

So the MMC controller that the WiFi chip is connected to is suddenly mmc0, not the one with the SD card slot. Looks like the order is random and probably depends on how fast the MMC controllers are responding. That explains why seemingly random changes to the system cause boot failures.

If you could try adding these statements to the aliases block dts file and check if it work then, I can just add another patch (probably best to do it for all Allwinner boards) and we're good. (Apparently the "correct" way to handle this is using UUIDs to mount file systems, I might have to look into that as well.)

CityAceE But these changes probably need to be made during the image build process. But I do not know how to do it.

If you have compiled an image already, the easiest way is probably to edit the dts file, then delete output/build/linux-6.6.21/.stamp_built and run make again.