<html> <head> <base href="https://bugs.freedesktop.org/" /> </head> <body> <div> <a class="bz_bug_link bz_status_NEW " title="NEW --- - [snb dp dongle] DP-to-dual-HDMI (link_train issue?)" href="https://bugs.freedesktop.org/show_bug.cgi?id=49402#c19">Comment # 19</a> on <a class="bz_bug_link bz_status_NEW " title="NEW --- - [snb dp dongle] DP-to-dual-HDMI (link_train issue?)" href="https://bugs.freedesktop.org/show_bug.cgi?id=49402">bug 49402</a> from <a class="email" href="mailto:ville.syrjala@linux.intel.com" title="Ville Syrjala <ville.syrjala@linux.intel.com>"> Ville Syrjala</a> <pre>(In reply to <a href="show_bug.cgi?id=49402#c18">comment #18</a>) > On Tue, 16 Apr 2013 09:50:53 +0000 > <a href="mailto:bugzilla-daemon@freedesktop.org">bugzilla-daemon@freedesktop.org</a> wrote: > > > <a class="bz_bug_link bz_status_NEW " title="NEW --- - [snb dp dongle] DP-to-dual-HDMI (link_train issue?)" href="show_bug.cgi?id=49402">https://bugs.freedesktop.org/show_bug.cgi?id=49402</a> > > > > --- <a href="show_bug.cgi?id=49402#c17">Comment #17</a> from Ville Syrjala <<a href="mailto:ville.syrjala@linux.intel.com">ville.syrjala@linux.intel.com</a>> --- > > I tried a few random things for this on IVB. > > > > - tried to send the training pattern and training lane set with one aux write > > instead of two. > > - tried to disable enhanced framing > > - tried to force some voltage swing/pre-emphasis values > > - tried with 6 bpc so that we'd get 1.62 links speed instead of 2.7 > > - tried to send post cursor2 traning values in case that would trick the sink > > into cooperation > > > > Unfortunately none of that helped. > > > > The BIOS produces a picture with the dongle, so I tried to compare some of the > > register values. The main differences I saw were that the BIOS uses auto > > training for FDI, some of the M/N values were different, and of course the BIOS > > also has panel fitter active since it's using a 720x400 resolution. > > The m/n values could definitely be a factor. Maybe our DP values are > slightly off and causing some skew in the dongle? It seems you are right. I just tried to hardcode the M/N values to the ones used by the BIOS, and now I get a picture on the screen. I'll just list the values here and hope someone else will figure out what code changes are needed to produce the working values ;) TU = 64 for both data M/N: BIOS: 62ae4e / 800000 i915: 65a360 / 83d600 link M/N: BIOS: 83931 / 80000 i915: 43c24 / 41eb0 The DP link training still "fails" the same way. It tries CR five times w/ vswing=0 and pre-emphasis=0 before giving up, and then goes on to the EQ phase which succeeds immediately. But the CR failure doesn't seem to prevent it from working.</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the QA Contact for the bug.</li> </ul> </body> </html>