[Bug 99093] New: [PNV] N450 and D510 machines get stuck in igt at gem_ringfill@basic-default-hang

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=99093

            Bug ID: 99093
           Summary: [PNV] N450 and D510 machines get stuck in
                    igt at gem_ringfill@basic-default-hang
           Product: DRI
           Version: DRI git
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: major
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: tomi.p.sarvela at intel.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Pineview testshosts I've tested seem to hang forever in following code when
tested with igt at gem_ringfill@basic-default-hang. Comment from vsyrjala implied
that the GPU hang reset messes PLL when done in wrong time.

No dmesg is left behind. This spot was found with gratuitous adding of
DRM_DEBUGs.

The bug has been around in drm-intel-nightly / drm-tip for at least two months.

drivers/gpu/drm/i915/i915_irq.c:i915_get_vblank_counter():

        /*
         * High & low register fields aren't synchronized, so make sure
         * we get a low value that's stable across two reads of the high
         * register.
         */
        do {
                high1 = I915_READ(high_frame) & PIPE_FRAME_HIGH_MASK;
                low   = I915_READ(low_frame);
                high2 = I915_READ(high_frame) & PIPE_FRAME_HIGH_MASK;
        } while (high1 != high2);

-- 
You are receiving this mail because:
You are the assignee for the bug.
You are the QA Contact for the bug.
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/intel-gfx-bugs/attachments/20161215/b774cd39/attachment.html>