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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_NEW "
title="NEW - third monitor doesn't work since commit "drm/i915: Remove the 8bpc shackles from DP MST""
href="https://bugs.freedesktop.org/show_bug.cgi?id=111505">bug 111505</a>
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<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>What</th>
<th>Removed</th>
<th>Added</th>
</tr>
<tr>
<td style="text-align:right;">Whiteboard</td>
<td>
</td>
<td>Triaged, ReadyForDev
</td>
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<td style="text-align:right;">CC</td>
<td>
</td>
<td>ville.syrjala@linux.intel.com
</td>
</tr>
<tr>
<td style="text-align:right;">Priority</td>
<td>not set
</td>
<td>highest
</td>
</tr></table>
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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW - third monitor doesn't work since commit "drm/i915: Remove the 8bpc shackles from DP MST""
href="https://bugs.freedesktop.org/show_bug.cgi?id=111505#c4">Comment # 4</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW - third monitor doesn't work since commit "drm/i915: Remove the 8bpc shackles from DP MST""
href="https://bugs.freedesktop.org/show_bug.cgi?id=111505">bug 111505</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>Considering this as a regression setting the priority to Highest.
(In reply to Geoffrey Bennett from <a href="show_bug.cgi?id=111505#c0">comment #0</a>)
<span class="quote">> Steps to reproduce the issue:
> - Fedora 30, Lenovo ThinkPad T480s laptop, internal + 2x external DisplayPort
> - External monitors: LG 24EB23 1920x1200 (DP-2-2) and LG 32UK550 3840x2160
> (DP-2-3)
> - Boot kernel commit f1477219869cc943ef9e0248b308da7b900c65ec or Fedora
> stock 5.2.9
> - At the LUKS password prompt, only two monitors display it (mirrored); the
> 3840x2160 monitor only displays a text cursor in the top-left
> - After logging in, the third monitor cannot be enabled
> - Boot kernel before the mentioned commit (or Fedora stock 5.1.19); all
> three monitors are working (mirrored password prompt)
>
> How often do these steps trigger the issue? Always.
>
> If I did the bisect right, this commit is the issue:
>
> commit f1477219869cc943ef9e0248b308da7b900c65ec
> Author: Ville Syrjälä <<a href="mailto:ville.syrjala@linux.intel.com">ville.syrjala@linux.intel.com</a>>
> Date: Tue Mar 26 16:25:53 2019 +0200
>
> drm/i915: Remove the 8bpc shackles from DP MST
>
> Allow DP MST to output any color depth. This means deep color as
> well as falling back to 6bpc if we would otherwise require too
> much bandwidth.
>
> TODO: We should probably extend bw_contstrained scheme to force
> all streams on the link to 6bpc if we can't fit the new stream(s)
> otherwise.
>
> Bad commit: f1477219869cc943ef9e0248b308da7b900c65ec
> Good commit: 765bdb0b3948747dda8c9bab300013e34f76fe88
>
> Comparing dmesg output between good & bad commits with drm.debug=0x1e ...
>
> Good commit, I see messages like:
>
> [ 7.215513] [drm:intel_atomic_check [i915]] hw max bpp: 30, pipe bpp: 24,
> dithering: 0
> [ 7.215977] [drm:intel_dump_pipe_config [i915]] cpu_transcoder: C, pipe
> bpp: 24, dithering: 0
> [ 7.216361] [drm:drm_dp_mst_atomic_check [drm_kms_helper]] [MST
> PORT:000000006766b031] requires 48 vcpi slots
> [ 7.216365] [drm:drm_dp_mst_atomic_check [drm_kms_helper]] [MST
> PORT:0000000048ae3b07] requires 14 vcpi slots
>
> Bad commit, I see messages like:
>
> [ 7.151412] [drm:intel_atomic_check [i915]] hw max bpp: 30, pipe bpp: 30,
> dithering: 0
> [ 7.151878] [drm:intel_dump_pipe_config [i915]] cpu_transcoder: C, pipe
> bpp: 30, dithering: 0
> [ 7.152272] [drm:drm_dp_mst_atomic_check [drm_kms_helper]] [MST
> PORT:00000000f27944b7] requires 60 vcpi slots
> [ 7.152276] [drm:drm_dp_mst_atomic_check [drm_kms_helper]] [MST
> PORT:00000000f43eff2e] requires 14 vcpi slots
> [ 7.152281] [drm:drm_dp_mst_atomic_check [drm_kms_helper]] [MST
> PORT:00000000f43eff2e] not enough VCPI slots in mst state 00000000c1ef406a
> (avail=3)
> [ 7.152293] [drm:drm_atomic_check_only [drm]] atomic driver check for
> 00000000a9c59397 failed: -28
>
> I also tested drm-tip, and neither external monitor worked then.</span >
@Ville, can you help here?</pre>
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