System Environment:
--------------------------
Arch:           i386
Platform:       Sandybridge
Kernel:     (drm-intel-next-queued)d7697eea3eec74c561d12887d892c53ac4380c00

Bug detailed description:
-------------------------
It happens on sandybridge with drm-intel-next-queued kernel.It works well on drm-intel-fixes kernel.
Bisect shows:05407ff889ceebe383aa5907219f86582ef96b72 is the first bad commit.
commit 05407ff889ceebe383aa5907219f86582ef96b72
Author:     Mika Kuoppala <mika.kuoppala@linux.intel.com>
AuthorDate: Thu May 30 09:04:29 2013 +0300
Commit:     Daniel Vetter <daniel.vetter@ffwll.ch>
CommitDate: Mon Jun 3 10:58:21 2013 +0200

    drm/i915: detect hang using per ring hangcheck_score

    Keep track of ring seqno progress and if there are no
    progress detected, declare hang. Use actual head (acthd)
    to distinguish between ring stuck and batchbuffer looping
    situation. Stuck ring will be kicked to trigger progress.

    This commit adds a hard limit for batchbuffer completion time.
    If batchbuffer completion time is more than 4.5 seconds,
    the gpu will be declared hung.

    Review comment from Ben which nicely clarifies the semantic change:

    "Maybe I'm just stating the functional changes of the patch, but in case
    they were unintended here is what I see as potential issues:

    1. "If ring B is waiting on ring A via semaphore, and ring A is making
       progress, albeit slowly - the hangcheck will fire. The check will
       determine that A is moving, however ring B will appear hung because
       the ACTHD doesn't move. I honestly can't say if that's actually a
       realistic problem to hit it probably implies the timeout value is too
       low.

    2. "There's also another corner case on the kick. If the seqno = 2
       (though not stuck), and on the 3rd hangcheck, the ring is stuck, and
       we try to kick it... we don't actually try to find out if the kick
       helped"

    v2: use atchd to detect stuck ring from loop (Ben Widawsky)

    v3: Use acthd to check when ring needs kicking.
    Declare hang on third time in order to give time for
    kick_ring to take effect.

    v4: Update commit msg

output:
filling ring
waiting
done waiting, check dmesg

dmesg:
[60161.225096] [drm:i915_driver_open],
[60161.225116] [drm:intel_crtc_set_config], [CRTC:3] [FB:27] #connectors=1 (x y) (0 0)
[60161.225120] [drm:intel_modeset_stage_output_state], [CONNECTOR:7:VGA-1] to [CRTC:3]
[60161.225122] [drm:intel_crtc_set_config], [CRTC:5] [NOFB]
[60161.225124] [drm:intel_modeset_stage_output_state], [CONNECTOR:7:VGA-1] to [CRTC:3]
[60161.225129] [drm:i915_driver_open],
[60171.239225] [drm:intel_crtc_set_config], [CRTC:3] [FB:27] #connectors=1 (x y) (0 0)
[60171.239231] [drm:intel_modeset_stage_output_state], [CONNECTOR:7:VGA-1] to [CRTC:3]
[60171.239233] [drm:intel_crtc_set_config], [CRTC:5] [NOFB]
[60171.239235] [drm:intel_modeset_stage_output_state], [CONNECTOR:7:VGA-1] to [CRTC:3]
[60171.239254] [drm:i915_driver_open],
[60171.239259] [drm:intel_crtc_set_config], [CRTC:3] [FB:27] #connectors=1 (x y) (0 0)
[60171.239261] [drm:intel_modeset_stage_output_state], [CONNECTOR:7:VGA-1] to [CRTC:3]
[60171.239262] [drm:intel_crtc_set_config], [CRTC:5] [NOFB]
[60171.239263] [drm:intel_modeset_stage_output_state], [CONNECTOR:7:VGA-1] to [CRTC:3]
[60171.239267] [drm:i915_driver_open],
[60176.787935] [drm:i915_hangcheck_elapsed] *ERROR* bsd ring: stuck on addr 0x3b4
[60176.788236] [drm:i915_error_work_func], resetting chip
[60176.790751] [drm:gm45_get_vblank_counter], trying to get vblank count for disabled pipe B
[60176.790883] [drm:ironlake_update_plane], Writing base 00072000 00000000 0 0 5120
[60176.790940] [drm:intel_crtc_set_config], [CRTC:3] [FB:27] #connectors=1 (x y) (0 0)
[60176.790944] [drm:intel_modeset_stage_output_state], [CONNECTOR:7:VGA-1] to [CRTC:3]
[60176.790946] [drm:intel_crtc_set_config], [CRTC:5] [NOFB]
[60176.790947] [drm:intel_modeset_stage_output_state], [CONNECTOR:7:VGA-1] to [CRTC:3]
[60176.801235] [drm:gmbus_xfer], GMBUS [i915 gmbus dpc] NAK for addr: 0050 r(1)
[60176.801239] [drm:drm_do_probe_ddc_edid], drm: skipping non-existent adapter i915 gmbus dpc
[60176.801259] [drm:intel_ironlake_crt_detect_hotplug], ironlake hotplug adpa=0x83f40018, result 1
[60176.801261] [drm:intel_crt_detect], CRT detected via hotplug
[60176.801909] [drm:gmbus_xfer], GMBUS [i915 gmbus dpc] NAK for addr: 0050 r(1)
[60176.801912] [drm:drm_do_probe_ddc_edid], drm: skipping non-existent adapter i915 gmbus dpc
[60176.801923] [drm:intel_ironlake_crt_detect_hotplug], ironlake hotplug adpa=0x83f40018, result 1
[60176.801924] [drm:intel_crt_detect], CRT detected via hotplug
[60176.802678] [drm:gmbus_xfer], GMBUS [i915 gmbus dpc] NAK for addr: 0050 r(1)
[60176.802680] [drm:drm_do_probe_ddc_edid], drm: skipping non-existent adapter i915 gmbus dpc
[60176.802691] [drm:intel_ironlake_crt_detect_hotplug], ironlake hotplug adpa=0x83f40018, result 1
[60176.802692] [drm:intel_crt_detect], CRT detected via hotplug

Reproduce steps:
----------------
1. ./gem_hangcheck_forcewake
2. dmesg -r | egrep "<[1-6]>" |grep drm