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    <body><span class="vcard"><a class="email" href="mailto:lakshminarayana.vudum@intel.com" title="Lakshmi <lakshminarayana.vudum@intel.com>"> <span class="fn">Lakshmi</span></a>
</span> changed
          <a class="bz_bug_link 
          bz_status_NEEDINFO "
   title="NEEDINFO - [Lenovo ThinkPad T450s] System hang with MST dock"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=103643">bug 103643</a>
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            <th>What</th>
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            <th>Added</th>
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           <td style="text-align:right;">Status</td>
           <td>REOPENED
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           <td>NEEDINFO
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            <b><a class="bz_bug_link 
          bz_status_NEEDINFO "
   title="NEEDINFO - [Lenovo ThinkPad T450s] System hang with MST dock"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=103643#c20">Comment # 20</a>
              on <a class="bz_bug_link 
          bz_status_NEEDINFO "
   title="NEEDINFO - [Lenovo ThinkPad T450s] System hang with MST dock"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=103643">bug 103643</a>
              from <span class="vcard"><a class="email" href="mailto:lakshminarayana.vudum@intel.com" title="Lakshmi <lakshminarayana.vudum@intel.com>"> <span class="fn">Lakshmi</span></a>
</span></b>
        <pre>(In reply to Johan ThorĂ©n from <a href="show_bug.cgi?id=103643#c19">comment #19</a>)
<span class="quote">> This error still occurs on kernel 4.20.

> My model is T470s and the behavior is consistent: It only happens when
> connected to an external display through the dock, not when using it
> disconnected from the dock. Can (most of the time) be triggered by changing
> display settings through xrandr.

> Dock model is SD20F82750.

> Dmesg error message:
> [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe B FIFO
> underrun

> GPU: Intel Corporation Skylake GT2 [HD Graphics 520] (rev 07)</span >

The original bug is reported is on Broadwell. So, your issue could be different
from the original issue reported in this bug.

Can you please attach the full dmesg log from boot with kernel parameters
drm.debug=0x1e log_buf_len=4M?

What is the impact of this issue other than the error in the log? Can you
elaborate the issue?</pre>
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