<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_NEW " title="NEW - [Regression]Multiple monitors via DP TB dock detection/resolution/layout failure after Skylake->Coffeelake upgrade" href="https://bugs.freedesktop.org/show_bug.cgi?id=111179#c10">Comment # 10</a> on <a class="bz_bug_link bz_status_NEW " title="NEW - [Regression]Multiple monitors via DP TB dock detection/resolution/layout failure after Skylake->Coffeelake upgrade" href="https://bugs.freedesktop.org/show_bug.cgi?id=111179">bug 111179</a> from <a class="email" href="mailto:ville.syrjala@linux.intel.com" title="Ville Syrjala <ville.syrjala@linux.intel.com>"> Ville Syrjala</a> <pre>I think the main issues is that your 4x5.4Gbps DP link doesn't have enough bandwidth to support two 4k@60 displays: [ 81.717461] [drm:drm_dp_mst_atomic_check [drm_kms_helper]] [MST PORT:000000006465ad61] requires 47 vcpi slots [ 81.717472] [drm:drm_dp_mst_atomic_check [drm_kms_helper]] [MST PORT:00000000fb13674f] requires 47 vcpi slots [ 81.717483] [drm:drm_dp_mst_atomic_check [drm_kms_helper]] [MST PORT:00000000fb13674f] not enough VCPI slots in mst state 000000006830e28e (avail=16) [ 81.717516] [drm:drm_atomic_check_only [drm]] atomic driver check for 000000004efe656f failed: -28 There is just no way to make that work. The only explanation I have why the SKL might have worked is that its TB implementation uses multiple DP links for the TB dock whereas the CFL uses just one link for whatever reason. The TB hardware supposedly is different between the two platforms. Our TB guru suggested that you should perhaps try to upgrade the TB firmware on the machine and see if that helps.</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the QA Contact for the bug.</li> <li>You are on the CC list for the bug.</li> <li>You are the assignee for the bug.</li> </ul> </body> </html>