Bug 94171

Created attachment 168731 [details]
possible fix

Please make sure your kernel has this patch:
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=72edd83cc9e5819ed1ee771519143d7594e059f0

Then apply this kernel patch on top of it.

Using the HD from the comment 0 system with the same cedar PCIe card installed in a slightly older P965 system , which has no onboard Intel gfx, both VGA-0 and DVI-0 outputs remain functional in X also with Mageia 4's kernel 3.14.32, as well as with all installations reported in comment 0, just as when using x600. IOW, no failures of x600 or cedar in the P965 system regardless of kernel.

Using the same x1300 in the P965 however, DVI-0 in X is always black and VGA-0 in X always works, in the installations using kernels newer than 3.14.32.

I subsequently retested the comment 0 system with the 2 of the same 3 ATI cards, but using a HD cloned from the original. Instead of using the same rv370 x600 of the original 3 I used an rv380 x600. Only the x1300 failed to produce X output on DVI-0, and only with kernels newer than 3.14.2, matching the behavior of the P965 system with all 3 ATI cards.

The fix works.  Tested by another user on this bug:
https://bugs.freedesktop.org/show_bug.cgi?id=89505
Just waiting for feedback from Christian.

Installed in a B85/Haswell/G3220 machine, the Cedar works as expected in openSUSE Tumbleweed with kernel 4.2.1 and openSUSE 13.1 with kernel 3.12.44 using:
xrandr --dpi 120 --output DVI-0 --mode 1920x1080 --above VGA-0 --output VGA-0 --primary --mode 1680x1050 # ati dual
but using X600 or X1300, both displays go black.

With Fedora 23, Plasma 5 and kernel 4.2.2, with X1300 the 1680x1050 screen on VGA-0 works as expected but the 1920x1080 screen on DVI-0 is black. With X600 and Cedar, all 1920x2130 works as expected.

Using
xrandr --dpi 120 --output HDMI1 --mode 1920x1080 --above VGA1 --output VGA1 --primary --mode 1680x1050 # intel dual
with the onboard video instead of X600, X1300 or Cedar, all OS/kernel combinations tried run Xorg as expected.

Created attachment 209811 [details]
Xorg.0.log F23 on big41, black DVI 1920x1080 output

On host big 41 in Fedora 21 with KDE4 and kernel 4.1.13 on Cedar booting multi-user.target, using startx and
xrandr --dpi 144 --output DVI-0 --mode 1920x1080 --above VGA-0 --output VGA-0 --primary --mode 1680x1050
both LCD screens play Xorg as expected, 1920x2130.

With
xrandr --dpi 144 --output DVI-0 --mode 1920x1080 --above VGA-0 --output VGA-0 --primary --mode 1920x1440
Xorg runs the LCD, where xrandr reports 1920x2520, as expected, but turns the CRT black. If I append --rate 75, which isn't required for expected results with Intel 4 Series or NVidia G84 gfxchips, then both displays work, comprising 1920x2520 as expected.

Still with CRT on VGA and LCD on DVI, startx with
xrandr --dpi 120 --output DVI-0 --mode 1920x1080 --above VGA-0 --output VGA-0 --primary --mode 1600x1200
produces 1920x2280 as expected in Xorg - no --rate parameter is required.

Fedora 23 with KDE5 and kernel 4.4.3 on same host with same three displays and Cedar mirrors exactly as herein described for Fedora 21.

Replacing the Cedar in big41 with rv516 X1300, and still using F23,
xrandr --dpi 144 --output DVI-0 --mode 1920x1080 --above VGA-0 --output VGA-0 --primary --mode 1920x1440
keeps the DVI's LCD black while in Xorg's expected 1920x2520, but working as expected on the ttys, even with
xrandr --dpi 120 --output DVI-0 --mode 1920x1080 --above VGA-0 --output VGA-0 --primary --mode 1600x1200
and even if appending --rate. With rv516, lowering demand all the way to
xrandr --dpi 108 --output DVI-0 --mode 1280x720 --above VGA-0 --output VGA-0 --primary --mode 1280x1024
is required to see output on the DVI portion of 1280x1744 on the LCD.