G5 Dual Head with x.org 6.8.2

Benjamin Herrenschmidt benh at kernel.crashing.org
Tue Sep 6 14:42:15 PDT 2005

On Tue, 2005-09-06 at 09:51 -0500, Eric Van Hensbergen wrote:
> Just upgraded the x.org installation on my G5.  I have dual 23" Cinema
> displays hooked up to a Radeon 9600 and have always had issues with
> getting X11 to use both monitors.  There are always two different
> problems:
> a) when I use the radeon driver versus the frame buffer, I always get
> lots of flickering and ghosting on the display.  In order to make this
> go away I apply the following patch to radeon_driver.c:

Only the second change should be necessary afaik. I made a fix in that
has been in CVS a while ago (but may not have made it to the stable
branch) that avoids odd dividers on the second PLL when the second head
is a flat panel. Can you check if that works for you ?
> The other problem I have is X not detecting the modes on the secondary
> monitor correctly.  This seems fixable by adding the following
> modeline to the second monitor on my /etc/X11/xorg.conf:
> Section "Monitor"
>         Identifier      "Apple Cinema 2"
>         Option          "DPMS"
>         Modeline "1920x1200"  155.00  1920 1984 2016 2144  1200 1203 1206 1212
> EndSection

Yes, old problem too. Might be fixed in CVS as well, I'd appreciate if
you could give it a try.

Also, if you are using 2 different monitors, you'll probably need to use
the ReverseDDC option. I also noticed that the TMDS table in the driver
doesn't do good with Apple 23" monitors, you should change it to

-    {{15000, 0xb0155}, {0xffffffff, 0xb01cb}, {0, 0}, {0, 0}},	/*CHIP_FAMILY_RV350*/
+    {{15500, 0xb0155}, {0xffffffff, 0xb01cb}, {0, 0}, {0, 0}},	/*CHIP_FAMILY_RV350*/

I'm not yet sure if it's safe to make that change permanently to the driver though.

> I don't know if there are any better fixes for these problems, but I
> figured I'd post my current solution here for anyone else experiencing
> the same problems.
>         -eric

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