[PORT] Help Porting U-BOOT master branch to GT90X V4 sun7i a20 tablet board

[Koray Bilir]

i got some more progress, i got the lvds panel and backlight working with
u-boot, i also switched to u-boot 2021.07-rc3-dirty, i have an mmc driver
enabled but so far it wasnt able to detect any sdcards that i plugged in
maybe the pin configs are wrong, i still havent tried configuring nand , i
migrated my build enviroment to a fresh install of debian 10 on a vm and my
build errors that i have encountered are gone so far.
heres an image of the working lvds panel :
https://drive.google.com/file/d/19-p3G8RATX2tDcESXd6cOlq55flDeED4/view?usp=sharing

Koray Bilir <koray509 at gmail.com>, 25 May 2021 Sal, 14:29 tarihinde şunu
yazdı:

> hello to the u-boot community, last week i wanted to do some hardware
> hacking and came across one of my nameless chinese brand sun7i a20 tablets
> poked around in adb shell, mounted the NANDA partition and to my surprise
> it was running u-boot v2011 , so i wanted to put a linux kernel on there to
> see if it would boot
> unfortunately the u-boot was outdated and couldn't boot it, tl dr; i am
> trying to write a device tree file so i can successfully port U-BOOT
> v2021.07-rc2-00238-geb53b943be-dirty.
> So far I have "successfully" compiled a u-boot.bin although binman gives
> an error of "cant find u-boot.dtb" the u-boot.bin works fine on the device.
> Sorry for my rambling. I just wanna give the most information in one post.
> so far I was able to write a simple .dts file for my board to get the
> debug uart ports working. luckily I discovered some test points on the
> board that were for uart tx rx.
> I got the uart interface working. I don't have an ftdi at the moment so
> i'm using an arduino as an usb to serial passthrough long story short i was
> able to get the u boot shell working
> and I was able to interface with the device. since its my first time cross
> compiling, u-boot and also device tree files i need some guidance to where
> should i look, one question that i have is
> Is there any pre-made building environments that I can just run on a
> virtual machine, im currently using my laptop which has debian 10 on it to
> compile and i'm not sure if I did everything right to get my build
> environment working. I have access to the stock rom of my device so i cant
> brick it and also i have access to the source code of the u-boot 2011
> version that was on the board from
> the factory. unfortunately this device has android 4.2.2 installed on it
> and i couldn't find any device tree files on it, i have the sysconfig.fex
> file that has the pinouts and config data on it
> So basically I'm trying to convert the sysconfig.fex to a dts file.
>
> my objectives right now are:
> setup ram correctly
> get nand working
> get sd/mmc working
> get usb working
> get 24bit lvds panel working
> get touchscreen working
> get audio working
> and finally get some sensors working that the board has
>
> I'm having no luck getting the nand and lvds panel working. I haven't
> tried sd/mmc , audio and touchscreen but i had usb working with some
> settings, i disabled it when i was debugging for other stuff.
> This gt90x v4 board is found in many nameless chinese tablets so I'm
> hoping this little project of mine can help others.
> also i see an unpopulated place that could take another nand chip , i'll
> have to try to see if it would work
> if any of you are interested in this or want to look at everything i got i
> can for the u-boot repository and commit my changes there and if any of you
> want to help you are more than welcome since
> this is my first time doing embedded stuff im learning as i go along so
> feel free to correct me.
> I can provide the source code of the 2011 u-boot that had everything
> working on the device and I can provide everything I have mentioned earlier
> (file wise).
>
> Let's get to the board details.
>
> ALLWINNER A20 SUN7I DUAL CORE CPU
> 2x NANYA MTT 256X16DDR3 V 1330 RAM CHIPS (device supposedly has 1gb of ram)
> TOSHIBA JP5415 TAIWAN 13359 A E / TC58TEG6DCJTA00 (8GB NAND)
> AXP209 0448CB 66K1
> GSL3680 64A0D4281N
> REALTEK RTL8188ETV D700331 GD27
> E203460 9INCH 1024X600 24BIT  LVDS PANEL
>
> Thats all of the major components on the board that i can see, i'll have
> an image of the board down below.
>
> https://drive.google.com/drive/folders/17zZTsgPHKktV4VARHAxR8tpHS4P04U7x?usp=sharing
>
> I would be super happy if anyone is able to point me in the right
> direction or help me.
>
> -Koray
>