Re: building image for Realtek RTS3916N mips SoC using vendor provided prebuilt external uClibc toolchain

davis roman <davis.roman84@...>

On Tue, Dec 28, 2021 at 10:09 PM Khem Raj <raj.khem@...> wrote:

On 12/28/21 2:53 PM, davis roman wrote:
Hi all,

I'm working on a project utilizing a Realtek RTS3916N mips SoC and as
part of Realtek's bsp offering, they provide their own fork of
buildroot packaged with their prebuilt binary toolchain.
I would much rather use yocto instead however Realtek made it clear
that no yocto support is available from their end and they have no
plans to provide it in the future.

In theory, I have Realtek's u-boot and kernel source so it should be
possible to build an image so long as poky is instructed to use an
external toolchain. This is where I hit my first road block because
Realtek only supports uClibc and I know the yocto community moved way
from uClibc, in favor of musl, since the Morty release. As a result, I
decided to use Krogoth-15.0.0 (knowing it's EOL) only because it
supports uClibc.

Now that I had picked a specific version of poky, I continued forward
with the EXTERNAL_TOOLCHAIN feature. The documentation references the
meta-sourcery layer as the typical use case. Using a sourcery
toolchain tarball ( 2014.05) I was able to build qemuarm/glibc
therefore as far as I can tell the EXTERNAL_TOOLCHAIN feature works as

Unfortunately, the issue I have now arises when I use the Realtek
toolchain. meta-sourcery informs me that building against uClibc is
not allowed as it has been blacklisted. Only glibc appears to be

I have looked around to see what other projects are similar and the
closest I can find is the creator CI20 however due to the Realtek
toolchain being based on uClibc, I haven't been able to find anything
suitable for my usecase.

I would greatly appreciate any suggestions regarding how to proceed
forward with yocto integration, using a mips uClibc based toolchain.
We have dropped uclibc support long time ago so any effort to support
uClibc based system will be a bit of work and we have also dropped stale
patches from metadata so even if you are able to get external toolchain
bolted in, you will unfurl next set of problems for yourself So I don't
have a better answer for you here, other than drop the idea of using
uclibc if you want to use modern yocto baseline. We did support it long
time ago so if you like you can use thise EOLed releases but there wont
be much support for it here on community mailing lists.
Thanks Khem for confirming my suspicions.

Is there any other course of action that I can try?
Since you have bootloader and kernel available to you, it might be less
work to put together a BSP layer and machine definition for this SOC
easily and it could be forward looking but there could be some
portability issues w.r.t. toolchain etc. which are manageable
here you will use internal mips toolchain to build your system and you
can use musl instead of uclibc to build the system or glibc is other
supported option.
I generated an internal mips toolchain built against musl and I tried
to compile u-boot but unfortunately, I'm getting "opcode not
supported" error messages.
If instead I use the realtek provided prebuilt toolchain then u-boot
compiles successfully.

I'm thinking that Realtek's toolchain has patches specific to their
SoC that have not been pushed upstream. Could this be the reason I'm
unable to compile uboot?

Thank you,


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