re: kern/49744: blank screen DL-360 radeon

[matthew green <mrg%eterna.com.au@localhost>]

The following reply was made to PR kern/49744; it has been noted by GNATS.

From: matthew green <mrg%eterna.com.au@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost,
    netbsd-bugs%netbsd.org@localhost, christos%netbsd.org@localhost
Subject: re: kern/49744: blank screen DL-360 radeon
Date: Sun, 26 Apr 2015 08:02:07 +1000

 >  The previously-noted hack/workaround adversely affects my ThinkPad A31p.
 >  It does not suffer from an almost-black-on-black framebuffer console
 >  display, but the hack still produces unpleasant color effects on the
 >  X display.
 
 hmmm, this is an RV200 chipset.  the RV250 in my old laptop doesn't
 work at all still, with the hack in place (to not set the LUT), i get
 correct green/white on black display, but X fails (AFAIK, the GPU
 never acknowledges a job completing, so X keeps asking in a loop.)
 
 if you remove the hack, what happens on your system?  this is in
 legacy_crtc_load_lut(), make sure you take the original code path
 (the 2nd loop, with 20/10/0 shifts.)  if that works OK, then we
 probably need to work on this hack better, since it isn't related
 to the actual chipset, but something else.   note that the macro
 "ASIC_IS_RV100" matches almost all the r100 and r200 chipsets.
 
 >  While tolerable for virtual terminasls (mine at least), it makes colored
 >  text on some simple web sites hard to read and graphics-rich websites
 >  practically unusable.
 
 the hack broke X11 for my RV280 card.  all my colours were wrong.
 having it run the original code makes it all happy.
 
 i've started looking at the older video-xf86-ati drivers to see if
 they can shed any light on the problem, but i've not gotten anything
 useful yet.  i did print the contents of the LUT registers before
 we break them, but it didn't seem to make sense to me, relative to
 what we expect to put there.  unfortunately, AMD never got the r100
 and r200 documentation released, so these existing drivers are really
 the only documentation we'll be able to find..
 
 
 .mrg.