[Bug 60606] vga_switcheroo / new Radeon DPM code mess up fbcon

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https://bugzilla.kernel.org/show_bug.cgi?id=60606

--- Comment #4 from Sebastien Fievet <sebastien.fievet@free.fr> ---
(In reply to Jani Nikula from comment #3)
I reverted the patch and double checked. The workaround is enough for me.
What I do is :
1. echo OFF > /sys/kernel/debug/vgaswitcheroo/switch at init time with a rc
script. Hence I always start on the IGD with the DIS OFF : 
  cat /sys/kernel/debug/vgaswitcheroo/switch
  0:DIS: :Off:0000:02:00.0
  1:DIS-Audio: :Off:0000:02:00.1
  2:IGD:+:Pwr:0000:00:02.0

2. to switch from IGD to DIS I do :
  for cmd in "ON MIGD DDIS"; do
    echo $cmd > /sys/kernel/debug/vgaswitcheroo/switch
  done
The screen flickers a bit during the OFF -> ON -> MIGD transition
  cat /sys/kernel/debug/vgaswitcheroo/switch
  0:DIS: :Pwr:0000:02:00.0
  1:DIS-Audio: :Pwr:0000:02:00.1
  2:IGD:+:Pwr:0000:00:02.0

3.I logout/login to X. To switch back to IGD I do :
  for cmd in "ON DIGD"; do
    echo $cmd > /sys/kernel/debug/vgaswitcheroo/switch
  done
The screen doesn't flicker.

=> I can cycle through IGD and DIS at will.

When testing your patch I was starting with both IGD and DIS ON. So initial
conditions were different :-(. Then :
1. echo DDIS > /sys/kernel/debug/vgaswitcheroo/switch worked, while without
your patch it didn't.
2. logout/login to X
  echo DIGD > /sys/kernel/debug/vgaswitcheroo/switch worked.
3. logout/login to X
  echo DDIS > /sys/kernel/debug/vgaswitcheroo/switch screwed up the display.

So I think I have been abused by the favourable initial conditions I used when
testing your patch. Let me know if you need anything else.

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