[Bug 35894] New: Displaying across 3 monitors with max resolution causes one monitor to enter power-saving mode (HD6870)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=35894

           Summary: Displaying across 3 monitors with max resolution
                    causes one monitor to enter power-saving mode (HD6870)
           Product: DRI
           Version: unspecified
          Platform: x86-64 (AMD64)
        OS/Version: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Radeon
        AssignedTo: dri-devel at lists.freedesktop.org
        ReportedBy: woogie at gmail.com


Using arandr, or KDE's RandR manager, I'm trying to adjust my display to
stretch across 3 monitors. One of the monitors enters power-saving mode when I
try this. Monitors are, from left to right:

DVI-1 (1680x1050 LCD)
DisplayPort-1 (1920x1080 LCD)
DVI-0 (1680x1050 LCD)

Configuring a desktop with all monitors set to their maximum resolution causes
one of the two DVI-connected monitors to enter power-saving mode. The mouse
cursor will still "disappear" into this monitor as if it were enabled. No error
messages appear in either X.org.log or dmesg. It is non-deterministic as to
which monitor turns off of the two DVI-connected monitors.

I can configure a desktop with, for example, 1280x1024, 1920x1080, 1280x1024
for resolutions (left to right) and all three monitors will function properly.
I cannot use 1680x1050, 1280x1024, 1680x1050, as one of the DVI monitors will
enter power saving mode. 

I have tested, and this hardware configuration will function with the
proprietary fglrx driver, and under Windows, so the card/monitors do not appear
at fault.

I have tried the 2.6.38 release candidate kernels, and this feature has never
functioned correctly, so I don't think it's a regression.

HARDWARE:
PowerColor HD6870
AMD 1075T
12Gb RAM
Asus M4A89/GTD-PRO USB3
DVI-1: LG Flatron W2242TQ
DisplayPort-1: Dell UV22H
DVI-0: ASUS (unknown)

OS:
ArchLinux, 64-bit with:
Kernel26, 2.6.38.2-1
xf86-video-ati 6.14.1-1
xorg-server 1.10.0.901-1
libdrm 2.4.24-1
ati-dri 7.10.1-1

Please let me know if I can provide any additional details. I am willing to
apply patches to the kernel or other packages as needed to test.

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