dfahren

@Jean-Francois Lessard
You won't believe it, but I found my error(s) ....
For the solution I had to look at the dts Paolo (https://github.com/paolosabatino/leds-fd6551) suggested in his code. I missed a line that effectively makes SDA really open-drain. However, pinctrl is not relevant in this context.
The fist line is bloody important, the second not so:
 
i2c-gpio,sda-output-only; i2c-gpio,scl-output-only; Although they do incur warnings in the kernel log, they are indispensable because without them, i2c signals don't reach the fd6551 controller.
 
Now everything works as expected. It shows (in fact, it showed ...) 88:88 right at the start and after that the actual time. Great!
I'm going to write a pull request for Nicolas' Github repo so that he can integrate it with the Armbian distribution.
I also edited your tm16xx source code to show 'boot' instead of 88:88, which is not my cup of tea.
You also have to make sure you compile the driver als built-in and not as a kernel object. So you get the 'boot' writing roughly around second 2.8 in the boot process when plugging in the mains adapter and this is early enough for me.
I attach all of the sources to this post. I hope you don't mind too much that I messed with your code and I apologize upfront.
 
Best wishes,
Deetsh
tm16xx_boot.c display-client-snippet.dts

@jock
Yes indeed, the driver written bei Jean-Francois is already integrated in Armbian by your patch, I know. Yes it works with the correct dts all is good. I struggled quite a bit until I arrived at the solution outlined in my last posting and I also wanted to have the writing 'boot' to show up right at the get-go in the LED line display. So I had to amend his driver a bit. 
One additional thing I could do to the driver is making the writing configurable in the dts, so that you only have to edit the text to show some other writing once the tv box boots up. This might be pretty easy, now I'm looking for some spare time ....

@Jean-Francois Lessard
You won't believe it, but I found my error(s) ....
For the solution I had to look at the dts Paolo (https://github.com/paolosabatino/leds-fd6551) suggested in his code. I missed a line that effectively makes SDA really open-drain. However, pinctrl is not relevant in this context.
The fist line is bloody important, the second not so:
 
i2c-gpio,sda-output-only; i2c-gpio,scl-output-only; Although they do incur warnings in the kernel log, they are indispensable because without them, i2c signals don't reach the fd6551 controller.
 
Now everything works as expected. It shows (in fact, it showed ...) 88:88 right at the start and after that the actual time. Great!
I'm going to write a pull request for Nicolas' Github repo so that he can integrate it with the Armbian distribution.
I also edited your tm16xx source code to show 'boot' instead of 88:88, which is not my cup of tea.
You also have to make sure you compile the driver als built-in and not as a kernel object. So you get the 'boot' writing roughly around second 2.8 in the boot process when plugging in the mains adapter and this is early enough for me.
I attach all of the sources to this post. I hope you don't mind too much that I messed with your code and I apologize upfront.
 
Best wishes,
Deetsh
tm16xx_boot.c display-client-snippet.dts

@dfahren 
I see that you have a lot to add here,
I would like you to participate in the integration of this board in Joshua Riek's project to enable RKNPU,
where the board already works but there is the problem of the maskrom button, micro stuttering and the memory clock.
 
edit: the u-boot 2025.01 for h96max v56 was merged, also wifi works out of the box, no patch needed. 
@maka @mvpwar @hzdm @dfahren @Vincenzoernst1 @pessimism
please keep a copy from next armbian release for this board.
 

@Hqnicolas    Thanks! Yes and yes. 😀
I'd like to have others test this u-boot, too, if you don't mind. In due time, you will get a PR for your repo and may include it in Armbian. However, I think it is too special for inclusion right into Armbian source code, but you can decide once you looked at the PR.