[Bug 48422] New: Radeon KMS fails on Radeon X850XT (R480) graphics card

[bugzilla-daemon@freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=48422

             Bug #: 48422
           Summary: Radeon KMS fails on Radeon X850XT (R480) graphics card
    Classification: Unclassified
           Product: DRI
           Version: XOrg 6.7.0
          Platform: x86-64 (AMD64)
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Radeon
        AssignedTo: dri-devel@lists.freedesktop.org
        ReportedBy: mike@coruscant.demon.co.uk


Created attachment 59628
  --> https://bugs.freedesktop.org/attachment.cgi?id=59628
Dmesg output from boot

Video output fails completely (apparently due to a KMS regression) on all
kernels >= 3.2, rendering the system unusable as a desktop. Access via SSH over
network is unaffected.

Steps to reproduce: Boot any recent kernel. This has been encountered with
Debian, and the kernel versions in question are:-

linux-image-3.0.0-2-amd64         3.0.0-5               functions as expected
linux-image-3.2.0-1-amd64         3.2.7-1               fails
linux-image-3.2.0-2-amd64         3.2.13-1              fails
linux-image-3.3.0-trunk-amd64     3.3-1~experimental.1  fails


Expected behaviour:-

At system boot, initial kernel output appears on the VGA console, until the drm
driver is loaded, when the kernel switches the output font and resolution. Boot
continues until a subsequent switch (I believe when the kernel attempts to
modeswitch the card), at which point the font visibly changes at this point and
boot continues, with further console output until the X desktop appears.

Actual behaviour with failing kernels:-

Boot starts normally until the modeswitch happens, at which point video output
ceases, and the monitor shows no signal on the DVI input.

Graphics hardware details from lspci is:-

01:00.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI R480
[Radeon X850XT (PCIE)] (Primary)
01:00.1 Display controller: Advanced Micro Devices [AMD] nee ATI R480 [Radeon
X850XT (PCIE)] (Secondary)

Attached file is dmesg output from booting the 3.3 kernel with drm.debug=0x6
passed as a kernel parameter.

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