if you want to rotate the display of your raspberry 7 inch touchscreen (with latest raspian) you need to do the following
- install xinput
sudo apt-get install xinput
- get the name of your display
xinput --list
- flip your display
xinput --set-prop 'FT5406 memory based driver' 'Coordinate Transformation Matrix' 0 -1 1 1 0 0 0 0 1
- add flipping to /boot/config.txt
display_rotate=1 (for 90 degrees)
- reboot
done!