[Bug 44121] New: Reproducible GPU lockup CP stall on Radeon HD 6450

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https://bugzilla.kernel.org/show_bug.cgi?id=44121

           Summary: Reproducible GPU lockup CP stall on Radeon HD 6450
           Product: Drivers
           Version: 2.5
    Kernel Version: 3.5-rc5
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Video(DRI - non Intel)
        AssignedTo: drivers_video-dri@kernel-bugs.osdl.org
        ReportedBy: khali@linux-fr.org
                CC: alexdeucher@gmail.com
        Regression: Yes


With kernels 3.5-rc3 to 3.5-rc5, I hit a GPU lockup CP stall issue whenever I
do some actions in Firefox: if I need to authenticate to access a given site,
or when the download target selection window pops up. I'm running Gnome 3.2 on
openSUSE 12.1.

When this happens, the whole Gnome interface freezes, with gnome-shell stuck at
100% CPU. In the kernel logs I see the following:

radeon 0000:08:00.0: GPU lockup CP stall for more than 10000msec
radeon 0000:08:00.0: GPU lockup (waiting for 0x00000000000113f3 last fence id
0x00000000000113f0)
radeon 0000:08:00.0: GPU softreset 
radeon 0000:08:00.0:   GRBM_STATUS=0xE55008A0
radeon 0000:08:00.0:   GRBM_STATUS_SE0=0xEC000001
radeon 0000:08:00.0:   GRBM_STATUS_SE1=0x00000007
radeon 0000:08:00.0:   SRBM_STATUS=0x200000C0
radeon 0000:08:00.0:   GRBM_SOFT_RESET=0x00007F6B
radeon 0000:08:00.0:   GRBM_STATUS=0x00003828
radeon 0000:08:00.0:   GRBM_STATUS_SE0=0x00000007
radeon 0000:08:00.0:   GRBM_STATUS_SE1=0x00000007
radeon 0000:08:00.0:   SRBM_STATUS=0x200000C0
radeon 0000:08:00.0: GPU reset succeed
[drm] PCIE GART of 512M enabled (table at 0x0000000000040000).
radeon 0000:08:00.0: WB enabled
radeon 0000:08:00.0: fence driver on ring 0 use gpu addr 0x0000000020000c00 and
cpu addr 0xffff88013557bc00
[drm] ring test on 0 succeeded in 0 usecs
[drm] ib test on ring 0 succeeded in 0 usecs

I have more samples if needed.

No problem when doing the same with kernel 3.4.4.

I ran "git bisect" and found that reverting the following commit fixes the
problem:

commit 416a2bd274566a6f607a271f524b2dc0b84d9106
Author: Alex Deucher <alexander.deucher@amd.com>
Date:   Thu May 31 19:00:25 2012 -0400

    drm/radeon: fixup tiling group size and backendmap on r6xx-r9xx (v4)

    Tiling group size is always 256bits on r6xx/r7xx/r8xx/9xx. Also fix and
    simplify render backend map. This now properly sets up the backend map
    on r6xx-9xx which should improve 3D performance.

    Vadim benchmarked also:
    Some benchmarks on juniper (5750), fullscreen 1920x1080,
    first result - kernel 3.4.0+ (fb21affa), second - with these patches:

    Lightsmark:   91 fps => 123 fps    +35%
    Doom3:        74 fps => 101 fps    +36%

    Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
    Signed-off-by: Jerome Glisse <jglisse@redhat.com>
    Signed-off-by: Dave Airlie <airlied@redhat.com>

Let me know if you need more debugging information, I'll do whatever I can to
help.

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