[U-Boot] u-boot on NAND sunxi

[Irvin Probst <probst@gmail.com>]

Hi,
I've been playing a bit with a pcduino3 board (A20), I know mainline 
u-boot has no R/W support on NAND for these boards and that's not what 
I'm asking for :-)

I've noticed that when I use an sdcard, u-boot+spl initializes the 
framebuffer and the screen goes on, whereas when I put u-boot.bin 
(without spl then) on the NAND the screen stays blank. Is there some 
magic done in the uboot's SPL that the defaut Allwinner's boot0/1 does 
not do ? The environment variables and  uboot's output are identical in 
both boot processes:

U-Boot 2016.03-dirty (Jun 28 2016 - 10:59:14 +0200) Allwinner Technology
[...]
HDMI connected: Setting up a 1280x1024 hdmi console (overscan 0x0)
In:    serial
Out:   vga
Err:   vga
[...]

The only difference is that the screen stays blank when uboot is read 
from the NAND by boot1. In this configuration booting linux (zImage+dtb 
read from a sdcard) afterwards does not bring the screen on either.

Any idea on what's going on ?

Thanks.