Bug 32282

I recently updated to this driver from 6.13.1, together with xorg-server-1.9.2 from 1.9.0.  On my 7500 and 9200se things generally looked much more stable (sporadic xorg crash, possibly in xscreensaver, seems to have gone, for which much thanks).

Then I went back to photo editing.  Many of my pics need a lot of editing to straighten them up, particularly perspective because the camera is often tilted. Suddenly, the gimp perspective tool had become unusable - the dialog window took much longer to appear, and I was lucky if I could move one of the controls (at the corners of the image) once, to view the effect, and generally unable to move two corners enough to get an acceptable result.

After misdiagnosis I've now reverted the system to a known good state, and tried the upgrades one by one, which is why I'm here.  The problem still exists in master (at b1af52e522158788a9613d6f1a2309a3987ad59f when I cloned it).

Bisection between 6.13.1 and 6.13.1 lead me to
f8fb9312d791af1f77020e8c2d35bb30841ed9aa is the first bad commit
commit f8fb9312d791af1f77020e8c2d35bb30841ed9aa
Author: Karl Tomlinson <karlt+@karlt.net>
Date:   Sun Aug 22 22:46:33 2010 +1200

    RADEONPrepareAccess_CS: fallback to DFS when pixmap is in VRAM
    
    This avoids costly CPU VRAM reads and lets EXA manage a system memory cache
    of the portions of pixmaps needed for unaccelerated operations.
    
    https://bugs.freedesktop.org/show_bug.cgi?id=27139

:040000 040000 94afde6673141f2976633cbba6a946e336856e5f d7184fa36bb29ec3fd00d564293c041efd132e18 M      src

If I revert that one commit from master, the perspective tool works ok again.

My card is
01:00.0 VGA compatible controller: ATI Technologies Inc Radeon RV200 QW [Radeon 7500] (prog-if 00 [VGA controller])
	Subsystem: Hightech Information System Ltd. Device 0207
	Flags: bus master, stepping, 66MHz, medium devsel, latency 32, IRQ 16
	Memory at f0000000 (32-bit, prefetchable) [size=128M]
	I/O ports at a000 [size=256]
	Memory at f8020000 (32-bit, non-prefetchable) [size=64K]
	[virtual] Expansion ROM at f8000000 [disabled] [size=128K]
	Capabilities: [58] AGP version 2.0
	Capabilities: [50] Power Management version 2
	Kernel driver in use: radeon