Overwriting dtbs on storage devices

[vali-um]

Hello,

As discussed in the forum the current u-boot setup in many cases overwrites the dtb on mmc. This seems to be done to support the different memory sizes and ethernet variations.
While it might be beneficial to do this for the in-memory dtb upon boot overwriting it on the storage medium itself is really bad. This file might be supplied by the user or distro and editing it will lead to confusion and issues.

The relevant code parts are https://github.com/starfive-tech/u-boot/blob/JH7110_VisionFive2_devel/include/configs/starfive-visionfive2.h#L151 and https://github.com/starfive-tech/u-boot/blob/JH7110_VisionFive2_devel/include/configs/starfive-visionfive2.h#L155

I'd suggest removing the write commands.
While looking at this i noticed the two branches do the same thing so the if statement could be removed to simplify the command.

Thanks,
Valentin

[MichaIng]

I totally agree with you, thanks for bringing this up here.

The only issue is that for 8 GiB and VisionFive 2 A1.2 Ethernet support, another solution would then need to be applied. If there is no way around adjusting the device tree nodes, then the best I could come up with are device tree overlays. With #44 they can be generally added via extlinux.conf.

• For 8 GiB support this is no big issue, I think, as having the SBC limited to 4 GiB does not cause issues.
• The Ethernet part however is nasty if one wants to access it via SSH right from the start. Of course another first boot service/script could read the serial number, derive revision and RAM size form it, and then apply the overlays automatically. However, no so great for distros to rely on such manual hacks.
• Another way is a boot.scr instead of extlinux.conf, which gives more flexibility on applying device trees or overlays based on model. But it feels like a step backwards.

See also short discussion here: http://forum.rvspace.org/t/loading-device-tree-overlays-on-vf2/2585/7?u=michaing

While looking at this i noticed the two branches do the same thing so the if statement could be removed to simplify the command.

I was recognising the same 👍.