[Arm-netbook] 2.7.4 preproduction sample, 1.7 MD, Questions

[Paul Boddie]

On Sunday, 19 July 2020 13:17:38 CEST Pablo Rath wrote:
> >On Sat, Jul 18, 2020 at 07:19:37PM +0200, Paul Boddie wrote:
> > I saw that there is a section about legacy U-Boot in the page:
> > 
> > http://rhombus-tech.net/allwinner/a20/EOMA68-A20_2-7-4_preproduction/
> 
> Yes, obviously I had to start with U-Boot first.
> Luke told me that sunxi U-Boot should build fine and that nothing has
> changed so I started there.
> 
> For mainline U-Boot I still need a valid config file to do 'make
> eoma68_foo_defconfig'. There is a .dts file here
> (http://rhombus-tech.net/allwinner/a20/boot/sun7i-a20-eoma68-a20.dts)
> but I don't know if it was used for mainline U-Boot and not just for
> Kernel compilation.

I'm not sure what the relationship is between U-Boot and Linux. My impression 
is that U-Boot borrows code from Linux, and there are benefits to U-Boot 
knowing about device tree files, but my own experiences with U-Boot 
development are rather limited.

[...]

> > So, what seems to be necessary is to get an older compiler and to use that
> > instead. Since distributions retire older compilers regularly, I used
> > Buildroot to create a suitable GCC 4.9 cross-compiler than can then build
> > the legacy U-Boot.
> 
> I have realised that on Debian gcc versions are kept installed. I have
> a native armhf installation (initially installed with Jessie) currently
> upgraded to stretch and gcc-4.9 is still installed. Changed between gcc
> versions with 'update-alternatives'. I don't know if this also apllies
> to cross-toolchains because my experience with crossbuilding is limited.
> 
> Sid (unstable) still has gcc-4.9 and even gcc-4.7 native armhf packages
> so this could be another solution I have not tested yes as I have no
> armhf sid installation.

It's useful to hear that GCC versions are kept around. Recently, I upgraded 
hardware and now have Debian Buster installed, and I think GCC 7 is about as 
old as the packages get. For cross-compilers, GCC 8 seems to be what is 
offered.

I did realise that you had probably managed just fine without having to find a 
toolchain, but it is probably useful to provide a path for others to follow as 
well.

[...]

> This is extremly helpful. I am going to try it out. Can you copy that to
> the wiki? Maybe as a separate subpage or at the end. I think we should
> keep everything short and clear for those who know what they are doing
> but still provide enough hand-holding and external context for those
> with less experience.

I'll try and add the recipes to the wiki. I was going to do so, but then found 
myself doing other things instead.

[...]

> Good news is that I made it to the sunxi U-Boot prompt on Friday. Booted
> via USB-FEL. So my
> soldered Pins, UART connection, Power Supply, µUSB-OTG on the card work
> fine.

Great!

> Next I have planned to compile a sunxi 3.4 Kernel and debootstrap a
> Debian rootfs.
> Then I want to try mainline U-Boot and a mainline Kernel.
> Feel free to share your solutions and best practices with me!

I'll try and take another look at this today. Hopefully, the old code can 
still be built without too many obstacles. The mainline code might present 
some challenges, at least with regard to specific hardware support.

Paul