I can run this two commands correctly
cvt 3840x2160 70
xrandr --newmode "3840x2160_70.00" 839.00 3840 4160 4584 5328 2160 2163 2168 2250 -hsync +vsync
But then when I try to add the mode to my device with
xrandr --addmode DP-4 "3840x2160_70.00"
It fails with the error
X Error of failed request: BadMatch (invalid parameter attributes)
Major opcode of failed request: 140 (RANDR)
Minor opcode of failed request: 18 (RRAddOutputMode)
Serial number of failed request: 45
Current serial number in output stream: 46
At this point arch wiki basically suggest me to ditch privative drivers and use nouveau. Any idea about how to debug this error? Thank you.