<html> <head> <base href="https://bugs.freedesktop.org/" /> </head> <body> <div> <a class="bz_bug_link bz_status_NEW " title="NEW - [SKL Bisected] eDP can not be lighted up after entering kernel" href="https://bugs.freedesktop.org/show_bug.cgi?id=89554#c36">Comment # 36</a> on <a class="bz_bug_link bz_status_NEW " title="NEW - [SKL Bisected] eDP can not be lighted up after entering kernel" href="https://bugs.freedesktop.org/show_bug.cgi?id=89554">bug 89554</a> from <a class="email" href="mailto:sonika.jindal@intel.com" title="Sonika <sonika.jindal@intel.com>"> Sonika</a> <pre>As per the VBT VBIOS doc, default value in VBT should be 1 and not 0. If we are setting it to 0 in VBT, it should be based upon the knowledge of the edp panel VswingPreEmphasisValue: 0 = Low Power Swing setting(200 mV) 1 = Default Swing settings(400 mV) I checked different versions of the GOP driver, and till 9.0.19, the default setting was 1, while from 9.0.20 (which Wendy is using), it changed the value to 0, which is not right. Then in the release notes of this gop driver I see, that it was added to fix one bug: <a href="https://vthsd.fm.intel.com/hsd/pcgsw/default.aspx#bug/default.aspx?bug_id=5642130">https://vthsd.fm.intel.com/hsd/pcgsw/default.aspx#bug/default.aspx?bug_id=5642130</a> >From the release notes: [DCN][4132577] : [BUG] 5642130 : Change default VBT Setting to use Low Vswing and Pre-emphasis for eDP display. : 9.0.1020 I strongly feel, we should not put a edp1.4 check there because its not related. For now, I would suggest to default it back to 1 in vbt and stitch a bios or use one version older bios with gop 9.0.19.</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> </ul> </body> </html>