downstream kernels with framebuffer: llvmpipe is miles faster than softpipe for software rendering.

Describe your issue

The default installation for plasma-mobile didn't work on my phone, since it only has a framebuffer driver, no drm. The wiki page tells people to edit /usr/bin/kwinwrapper to set the --framebuffer option and add some exports. After changing it, the UI was literally unusable (sub 0.5 fps, most of the times more like 0.1). After changing export GALLIUM_DRIVER=softpipe to export GALLIUM_DRIVER=llvmpipe, or just removing it, it became usable performance wise (something like 10-20fps). (Has other issues mostly specific for this device but that's a story for an other day)

The wiki has a section a bit before that saying this:

	# NOTE: using GALLIUM_DRIVER=llvmpipe might give you better performance (or not work at all.)
	# If it does give you a performance gain, please open an issue to discuss how to implement this properly.

So that's what I'm doing now! I think the wiki should be clear about this at the software rendering section too, and I think the script should fall back to framebuffer if drm isn't found. I don't know about the "(or not work at all.)" part though. Is this known to fail on some devices? Can't we somehow fall back to softpipe if llvmpipe fails in that case?

How to reproduce your issue?

Try llvmpipe and softpipe on plasma-mobile (and probably any environment and opengl app) and see the difference.

What device are you using?

samsung-jackpotlte

On what postmarketOS version did you encounter the issue?

• edge (master branch)
• stable (v20.05 branch)

On what environment did you encounter the issue?

Phone environments

• Phosh
• Plasma Mobile
• Sxmo

Other

• No environment
• GNOME
• KDE Plasma
• Kodi
• MATE
• Shelli
• Sway
• Weston
• Xfce4
• fbkeyboard
• i3wm

How did you get postmarketOS image?

• from https://images.postmarketos.org
• I built it using pmbootstrap
• It was preinstalled on my device

What's the build date of the image? (in dd-mm-yyyy format)

29-10-2020