This issue was seen 4 times in last 6 months. Last time this issue occurred 4 months ago.
I assume this issue has been Resolved/fixed and Closing now. Feel free to reopen if you still have the issue.

Guess who's back (or never really left)?

https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_4971/shard-kbl2/igt@kms_flip@basic-flip-vs-dpms.html

<3> [200.850023] [drm:intel_dp_start_link_train [i915]] *ERROR* failed to start channel equalization

OK, now this is odd: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_4975/shard-kbl2/igt@kms_chv_cursor_fail@pipe-b-64x64-left-edge.html

<3> [154.619909] [drm:intel_dp_start_link_train [i915]] *ERROR* failed to start channel equalization

Two in a row? Sounds like a regression to me!

A CI Bug Log filter associated to this bug has been updated:

{- shard-kbl: All tests - dmesg-warn - *ERROR* failed to start channel equalization -}
{+ shard-apl shard-kbl: All tests - dmesg-warn - *ERROR* failed to start channel equalization +}

New failures caught by the filter:

* https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_5622/shard-apl7/igt@pm_rpm@gem-execbuf-stress-extra-wait.html

A CI Bug Log filter associated to this bug has been updated:

{- shard-apl shard-kbl: All tests - dmesg-warn - *ERROR* failed to start channel equalization -}
{+ APL KBL: All tests - dmesg-warn - *ERROR* failed to start channel equalization +}

New failures caught by the filter:

  * https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_5978/fi-apl-guc/igt@i915_pm_rpm@module-reload.html

Displayport (DP) requires that we equalize the cable losses by selecting the best combination of voltage swing and pre-emphasis values. These are essential parameters to keep signal quality as high level as possible between the sink and the source. Failing to due so, will lead corrupted image in form of frame losses or in worst case scenario no image at all.

#assessment

This issue seems to occur most frequently on shard-kbl2 machine 2-3 times every month. It has been observed on shard-kbl1 and two apl machines once in a year. It is possible that this may be due to faulty hardware.

-- GitLab Migration Automatic Message --

This bug has been migrated to freedesktop.org's GitLab instance and has been closed from further activity.

You can subscribe and participate further through the new bug through this link to our GitLab instance: https://gitlab.freedesktop.org/drm/intel/issues/78.