xrandr --listproviders
Providers: number : 3
Provider 0: id: 0x78 cap: 0x9, Source Output, Sink Offload crtcs: 2 outputs: 3
associated providers: 2 name:radeon
Provider 1: id: 0x43 cap: 0x6, Sink Output, Source Offload crtcs: 4 outputs: 0
associated providers: 2 name:radeon
Provider 2: id: 0x43 cap: 0x6, Sink Output, Source Offload crtcs: 4 outputs: 0
associated providers: 2 name:radeon

glxinfo | grep "OpenGL renderer"
OpenGL renderer string: Gallium 0.4 on AMD SUMO2

But when I tried:

xrandr --setprovideroffloadsink 0x78 0x43
X Error of failed request:  BadValue (integer parameter out of range for
operation)
  Major opcode of failed request:  140 (RANDR)
  Minor opcode of failed request:  34 ()
  Value in failed request:  0x78
  Serial number of failed request:  17
Current serial number in output stream:  18