Tegra2_TRM_DP04508001v01p.pdf 

I will try to collect useful stuff about Tegra latest upstream source on this page.
Nvidia Tegra 2/3 APX/nv3p protocol implementation
• https://github.com/AndroidRoot/wheelie 
qemu
https://github.com/digetx/tegra2_qemu 
i2cdetect
root@ac100:~# i2cdetect -l
i2c-1   i2c             7000c400.i2c                            I2C adapter
i2c-2   i2c             7000d000.i2c                            I2C adapter
i2c-0   i2c             7000c000.i2c                            I2C adapter
root@ac100:~# i2cdetect -y 0                                                                                                                                                 
Error: Can't use SMBus Quick Write command on this bus                                                                                                                       
root@ac100:~# i2cdetect -F 0                                                                                                                                                 
Functionalities implemented by /dev/i2c-0:                                                                                                                                   
I2C                              yes                                                                                                                                         
SMBus Quick Command              no                                                                                                                                          
SMBus Send Byte                  yes                                                                                                                                         
SMBus Receive Byte               yes                                                                                                                                         
SMBus Write Byte                 yes                                                                                                                                         
SMBus Read Byte                  yes                                                                                                                                         
SMBus Write Word                 yes                                                                                                                                         
SMBus Read Word                  yes                                                                                                                                         
SMBus Process Call               yes                                                                                                                                         
SMBus Block Write                yes                                                                                                                                         
SMBus Block Read                 no
SMBus Block Process Call         no
SMBus PEC                        yes
I2C Block Write                  yes
I2C Block Read                   yes
root@ac100:~# i2cdetect -y -r 0
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- UU -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 4f 
50: 50 51 52 53 54 55 56 57 -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --

grate‑driver tegra2 support for mainline
https://github.com/grate‑driver 
https://github.com/grate‑driver/grate/wiki/Grate‑driver 
https://wiki.debian.org/CreatePackageFromPPA

https://code.launchpad.net/~grate-driver/+archive/ubuntu/ppa

sudo apt install devscripts build-essential software-properties-common

sudo add-apt-repository ppa:grate-driver/ppa

# enable only deb-src (suggested beaver doesn't work for me)

root@tegra20:/home/dpavlin# cat /etc/apt/sources.list.d/grate-driver-ubuntu-ppa-disco.list 
#deb http://ppa.launchpad.net/grate-driver/ppa/ubuntu beaver main
deb-src http://ppa.launchpad.net/grate-driver/ppa/ubuntu disco main

apt update # make sure that is pass, use apt-key adv --recv-key if needed

# build order is important

apt-get build-dep libdrm
apt source --build libdrm
dpkg -i libdrm*.deb

apt-get build-dep xserver-xorg-video-opentegra

apt source --build xserver-xorg-video-opentegra

# this will fail to instal because of libturbojpg dependency

root@x200:/home/dpavlin/grade-build/xserver-xorg-video-opentegra-201901152016~grate~feac058~ubuntu19.04.1# vi debian/control

Package: xserver-xorg-video-opentegra
Architecture: armhf
Depends: ${shlibs:Depends}, ${misc:Depends}, ${xviddriver:Depends},
 libdrm-tegra0, liblz4-1, libturbojpeg0 (>= 1.5.0), libpng16-16,
Provides: ${xviddriver:Provides}
Description: X.Org X server -- Opensource driver for NVIDIA Tegra.
 This package provides HW-accelerated opensource driver for NVIDIA
 Tegra20+ SoC's from the GRATE project <URL:https://github.com/grate-driver>.

root@x200:/home/dpavlin/grade-build/xserver-xorg-video-opentegra-201901152016~grate~feac058~ubuntu19.04.1# dpkg-buildpackage

root@tegra20:/home/dpavlin# apt-get install x11-xserver-utils

root@tegra20:/etc# git diff
diff --git a/X11/xinit/xserverrc b/X11/xinit/xserverrc
index 94494ec..e6c4aa4 100755
--- a/X11/xinit/xserverrc
+++ b/X11/xinit/xserverrc
@@ -1,3 +1,3 @@
 #!/bin/sh
 
-exec /usr/bin/X -nolisten tcp "$@"
+exec /usr/bin/X -listen tcp "$@"

# let's try it

startx

root@tegra20:/home/dpavlin# export DISPLAY=:0
root@tegra20:/home/dpavlin# xhost +
access control disabled, clients can connect from any host

# on another computer

dpavlin@x200:~$ x2x -to tegra20:0 -south

# and one flip of display later, I have working X11 with remote mouse and keyboard

root@tegra20:/home/dpavlin# xrandr --output LVDS-0 --rotation inverted

# to get mesa to compile beause of dependencies, I needed to update to buster

root@tegra20:/home/dpavlin# apt-get build-dep mesa
Reading package lists... Done
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 builddeps:mesa : Depends: debhelper (>= 11) but 10.2.5 is to be installed
                  Depends: quilt (>= 0.63-8.2~) but it is not going to be installed
                  Depends: x11proto-dev but it is not installable
                  Depends: libxcb-dri3-dev (>= 1.13) but it is not going to be installed
                  Depends: libxcb-present-dev (>= 1.13) but it is not going to be installed
                  Depends: llvm-7-dev (>= 1:7~) but it is not installable
                  Depends: libwayland-dev (>= 1.15.0) but 1.12.0-1 is to be installed
                  Depends: libwayland-egl-backend-dev (>= 1.15.0) but it is not installable
                  Depends: libclang-7-dev (>= 1:7~) but it is not installable
                  Depends: libclc-dev (>= 0.2.0+git20180917-1~) but it is not going to be installed
                  Depends: wayland-protocols (>= 1.9) but it is not going to be installed
                  Depends: libglvnd-core-dev but it is not installable
E: Unable to correct problems, you have held broken packages.

# after buster upgrade and rebuild of everything

(with dpkg-buildpackage)

root@tegra20:/home/dpavlin/grade-build# apt source --build mesa

dpkg -i *.deb

~50 fps with 25% cpu usage in glxgears

root@tegra20:/home/dpavlin/grade-build# apt-get build-dep libvdpau-tegra
Reading package lists... Done
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 builddeps:libvdpau-tegra : Depends: libdri2-dev but it is not installable
E: Unable to correct problems, you have held broken packages.

# sigh

root@tegra20:/home/dpavlin/grade-build# apt source --build libvdpau-tegra
...
dpkg-checkbuilddeps: error: Unmet build dependencies: libxv-dev libdri2-dev

root@tegra20:/home/dpavlin/grade-build# apt --fix-broken install
root@tegra20:/home/dpavlin/grade-build# apt-get install libxv-dev

root@tegra20:/home/dpavlin/grade-build/libvdpau-tegra-201901220047~grate~8efb41c~ubuntu18.10.1# vi debian/control 

remove libdri2-dev and libdri2

root@tegra20:/home/dpavlin/grade-build/libvdpau-tegra-201901220047~grate~8efb41c~ubuntu18.10.1# dpkg-buildpackage

dpkg -i ../libvdpau-tegra*.deb

partition table support
https://lkml.org/lkml/2020/2/24/1358