[Bug 49351] New: vga_switcheroo results in black screen (bisected)

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=49351

           Summary: vga_switcheroo results in black screen (bisected)
           Product: Drivers
           Version: 2.5
    Kernel Version: 3.7-rc1+
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Video(DRI - non Intel)
        AssignedTo: drivers_video-dri at kernel-bugs.osdl.org
        ReportedBy: e-mail at date.by
                CC: alexdeucher at gmail.com
        Regression: Yes


Created an attachment (id=84381)
 --> (https://bugzilla.kernel.org/attachment.cgi?id=84381)
lspci -vvv

On my muxed hybrid system (Lenovo IdeaPad U455) vga_switcheroo doesn't work as
expected. Initially after system booting both video cards are powered and the
IGD one is active. Then, when i try to switch active gpu with

 # echo DIS > /sys/kernel/debug/vgaswitcheroo/switch

screen goes black.
The first bad commit, that broke vga_switcheroo is:

commit 492b49a2f21a7ce6cb0abce36017daa06036a626
Author: Alex Deucher <alexander.deucher at amd.com>
Date:   Thu Aug 16 14:07:37 2012 -0400

    drm/radeon: reorganize ATPX support (v2)

    - rework the acpi execute code
    - User proper parameters for ATPX functions

    v2: rebase fixes

    Signed-off-by: Alex Deucher <alexander.deucher at amd.com>

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