ATI video problem - extremely slow desktop - 100% cpu load

[Vincent Stemen]

Hi.  

I also posted about this problem on the FreeBSD mailing list.

FreeBSD 11.1-RELEASE
Motherboard:    gigabyte GA-78LMT-USB3 R2
Video:          Integrated ATI Radeon HD 3000 graphics

I have also tested with two additional ATI cards.
A Radeon HD 5450 and and older card that shows as
"RV370 [Radeon X300 SE]" in the PCI info.

Same problem on all of them.

System runs fine with a simple stand alone window manager such as jwm, 
openbox, etc.  But anytime I run a desktop environment that has a panel and/or
desktop icons, the X desktop takes a very long time to start up and runs
extremely slow and unresponsive, the pointer jumps instead of moving smoothly,
and the main Xorg process runs at 100% load on one core.  I have tried several
different desktops, such as xfce, enlightenment, lumina, etc.  Similar problem
on all of them.

The weird thing is that, every once in a while, when I launch X, it comes up
quick and runs fine.  Shut down X and re-run it and it's back doing it again.
Once it comes up working correctly, it stays working until I restart X.

I have tried re-installing all the ports from X11 and the desktop environments
from FreeBSD 11 release_1, release_2, quarterly, and latest.  Same problem
with all of them.

Does anybody have any idea what could be causing this?

I don't know if for sure if this is a FreeBSD or an xorg problem.  Here are
radeon kernel modules running when running on the Radeon HD 3000.

# kldstat

   5    1 0xffffffff82431000 12b4a0   radeonkms.ko
   ...
  10    1 0xffffffff825b9000 103e     radeonkmsfw_RS780_pfp.ko
  11    1 0xffffffff825bb000 5b3f     radeonkmsfw_RS780_me.ko
  12    1 0xffffffff825c1000 1338     radeonkmsfw_R600_rlc.ko

X is using the ati driver from the xf86-video-ati-7.9.0_1,1 package.

The evidence points stongly toward it being an ATI driver problem.  If I edit
/etc/X11/xorg.conf to use the "vesa" driver rather than the "radeon" driver the
problem goes away.

But, of course, the vesa driver is low resolution and does not re-initialize the
console when I exit X.