Dual link on X1250 radeonhd git head fails

[Alex Deucher]

On Thu, Mar 27, 2008 at 1:46 AM, Adam J. Richter <adam at yggdrasil.com> wrote:
>
> On Thu, Mar 20, 2008 at 10:05:39AM -0400, Alex Deucher wrote:
>  > On Thu, Mar 20, 2008 at 2:51 AM, Adam J. Richter <adam at yggdrasil.com> wrote:
>  > > On Mon, Mar 17, 2008 at 02:42:40PM +0100, Matthias Hopf wrote:
>  > >  > Current git of radeonhd should support dual link DVI as well, though
>  > >  > this is untested ATM.
>  > >
>  > >         I just tried the radeonhd git head (pulled minutes ago) on a
>  > >  30 inch 2560x1600 HP lp3065 monitor, and the screen is black with the
>  > >  green LED flashing.  This same screen displays BIOS messages, lilo
>  > >  text and the character mode linux console fine, as I think there is
>  > >  some built in video stretching done in character mode (for example, in
>  > >  character mode, my 1920x1200 monitor always claims to be receiving a
>  > >  1920x1200 signal rather than 640x480 or something similar that one
>  > >  would normally associate with character mode).  xrandr, correctly
>  > >  describes the video modes for my 1920x1200 monitor on the VGA cable
>  > >  and the 2560x1600 monitor on VGA, and indicates that 2560x1600 is
>  > >  selected, and the virtual screen size is expanded to 2560x1600.  So, I
>  > >  think this is a mode setting issue and not some misconfiguration on my
>  > >  part.
>  > >
>  > >         My new lp3065 can select between three dual-link DVI input
>  > >  cables, so I should be able to plug it into an nvidia card for now to
>  > >  use it immediately while still being available to test new changes
>  > >  through a cable connect to my AMD motherboard.  So, if anyone wants me
>  > >  to try a patch and report results, I am happy to do so when I have time.
>  > >
>  > >         Also, if anyone would like to point me to the relevant page
>  > >  numbers of the recently released X docs for the rs690 in
>  > >  http://www.x.org/docs/AMD/ for enabling dual link, I may be able to
>  > >  try to work on this myself during the weekend.  I had previously
>  > >  skimmed AMD's recently released documents but didn't immediately find
>  > >  a bit to set to activate dual link.
>  >
>  > Have you tried radeon?
>
>         Yes.  With either radeon or radeonhd drivers, xrandr correctly
>  notes that 2560x1600 video mode is available, and that mode can be
>  selected with xrandr, but the video does not display correctly.  The
>  way the video is incorrect differs between radeonhd and radeon.  With
>  radeonhd, the screen displays a slowly changing rectangular pattern.
>  With radeon, the LED in the corner of the monitor changes from green
>  to orange and the screen is black.
>
>         The above statements are true for the git versions of radeon
>  and readeonhd both as of a couple of days ago and as of git pulls from
>  about an hour ago.
>

You might try a slightly lower pixel clock.  One user reported that
his 1920x1200 monitor works at 150 Mhz but has problems at 154 Mhz
which is the clock of the preferred mode.  try something like:

Modeline "2560x1600_58.50"  261.75  2560 2608 2640 2720  1600 1603
1609 1645  +HSync -Vsync

You might also want to fiddle around with some alternate timings.

Alex