On Wed, 16 May 2018, Manasi Navare <manasi.d.nav...@intel.com> wrote: > On Wed, May 16, 2018 at 10:21:10AM -0700, Lucas De Marchi wrote: >> This reverts commit c0cfb10d9e1de490e36d3b9d4228c0ea0ca30677. >> >> This fails on a Dell XPS13 9350 machine giving me just a black screen. >> [drm:intel_dp_start_link_train [i915]] [CONNECTOR:59:eDP-1] Link Training >> Passed at Link Rate = 540000, Lane count = 4 >> [drm:intel_dp_start_link_train [i915]] *ERROR* [CONNECTOR:59:eDP-1] Link >> Training failed at link rate = 540000, lane count = 4 >> [drm:intel_dp_start_link_train [i915]] [CONNECTOR:59:eDP-1] Link Training >> Passed at Link Rate = 540000, Lane count = 4 >> [drm:intel_dp_start_link_train [i915]] [CONNECTOR:59:eDP-1] Link Training >> Passed at Link Rate = 540000, Lane count = 4 >> [drm:intel_dp_start_link_train [i915]] [CONNECTOR:59:eDP-1] Link Training >> Passed at Link Rate = 540000, Lane count = 4 >> [drm:intel_dp_start_link_train [i915]] *ERROR* [CONNECTOR:59:eDP-1] Link >> Training failed at link rate = 540000, lane count = 4 >> [drm:intel_dp_start_link_train [i915]] *ERROR* [CONNECTOR:59:eDP-1] Link >> Training failed at link rate = 540000, lane count = 4 >> [drm:intel_dp_start_link_train [i915]] [CONNECTOR:59:eDP-1] Link Training >> Passed at Link Rate = 540000, Lane count = 4 >> [drm:intel_dp_start_link_train [i915]] *ERROR* [CONNECTOR:59:eDP-1] Link >> Training failed at link rate = 540000, lane count = 4 >> [drm:intel_dp_start_link_train [i915]] [CONNECTOR:59:eDP-1] Link Training >> Passed at Link Rate = 540000, Lane count = 4 >> [drm:intel_dp_start_link_train [i915]] [CONNECTOR:59:eDP-1] Link Training >> Passed at Link Rate = 540000, Lane count = 4 >> [drm:intel_dp_start_link_train [i915]] *ERROR* [CONNECTOR:59:eDP-1] Link >> Training failed at link rate = 540000, lane count = 4 >> >> On a working kernel, previous to this commit I have: >> [drm:intel_dp_start_link_train [i915]] [CONNECTOR:59:eDP-1] Link Training >> failed at link rate = 540000, lane count = 4 >> [drm:intel_dp_start_link_train [i915]] [CONNECTOR:59:eDP-1] Link Training >> Passed at Link Rate = 270000, Lane count = 4 >> >> Cc: Clinton Taylor <clinton.a.tay...@intel.com> >> Cc: Jim Bride <jim.br...@linux.intel.com> >> Cc: Jani Nikula <jani.nik...@linux.intel.com> >> Cc: Ville Syrjala <ville.syrj...@linux.intel.com> >> Cc: Dave Airlie <airl...@redhat.com> >> Cc: Daniel Vetter <daniel.vet...@ffwll.ch> >> Cc: Manasi Navare <manasi.d.nav...@intel.com> >> Cc: Ville Syrjala <ville.syrj...@linux.intel.com> >> Cc: Imre Deak <imre.d...@intel.com> >> Signed-off-by: Lucas De Marchi <lucas.demar...@intel.com> >> --- >> >> I'm sending this for reference and discussion only, but it doesn't seem >> to be the right fix. Not only because it would mean IGT failing on CI, >> but also because we seem to be having several link training running >> concurrently and the last one failing leaves the panel at that state. > > I just looked at the full log of the failing case and in that case it > first tries training at the highest link rate, lane count for eDP and > passes before enabling pipe A. But then the panel soon sends a short > pulse indicating loss of signal which causes the driver to call > intel_dp_check_link_status() where drm_dp_channel_eq_ok() check fails > and thats why you see multiple link training attempts there which fail > and eventually result in a black screen.
We also have a bug [1] where the link training succeeds after the hpd, but the display starts to flicker. [1] https://bugs.freedesktop.org/show_bug.cgi?id=105267 > Now in case of passing case, whats interesting is that it starts with > same highest link rate 5.4Gbps but fails the very first time and now > the fallback code kicks in and lowers the link rate to 2.7Gbps. Now > in this particular case, the edp panel's native resolution of 3200 x > 1800 fits even for the lowered link rate of 2.7Gbps and it retrains at > that and passes so we get a recovered modeset. > > So I am thinking because of such cases, we should probably not asusme > that the native mode will not fit the lowered fallback link rate. So I > guess we should still try fallback for eDP as long as its not pruning > the native mode on the panel. > > Alternatively I think if we start from lowest link rate and lane count > like we do for DP then it will pick the lowest possible link rate > required for the native mode and we might not run into this situation. > > Jani, Ville any thoughts on which approach should be chosen? See [2]. BR, Jani. [2] http://marc.info/?i=87sh6qzqpp....@intel.com > > Regards > Manasi > >> >> drivers/gpu/drm/i915/intel_dp_link_training.c | 26 +++++++------------ >> 1 file changed, 9 insertions(+), 17 deletions(-) >> >> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c >> b/drivers/gpu/drm/i915/intel_dp_link_training.c >> index f59b59bb0a21..78f1fe934da3 100644 >> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c >> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c >> @@ -330,22 +330,14 @@ intel_dp_start_link_train(struct intel_dp *intel_dp) >> return; >> >> failure_handling: >> - /* Dont fallback and prune modes if its eDP */ >> - if (!intel_dp_is_edp(intel_dp)) { >> - DRM_DEBUG_KMS("[CONNECTOR:%d:%s] Link Training failed at link >> rate = %d, lane count = %d", >> - intel_connector->base.base.id, >> - intel_connector->base.name, >> - intel_dp->link_rate, intel_dp->lane_count); >> - if (!intel_dp_get_link_train_fallback_values(intel_dp, >> - >> intel_dp->link_rate, >> - >> intel_dp->lane_count)) >> - /* Schedule a Hotplug Uevent to userspace to start >> modeset */ >> - schedule_work(&intel_connector->modeset_retry_work); >> - } else { >> - DRM_ERROR("[CONNECTOR:%d:%s] Link Training failed at link rate >> = %d, lane count = %d", >> - intel_connector->base.base.id, >> - intel_connector->base.name, >> - intel_dp->link_rate, intel_dp->lane_count); >> - } >> + DRM_DEBUG_KMS("[CONNECTOR:%d:%s] Link Training failed at link rate = >> %d, lane count = %d", >> + intel_connector->base.base.id, >> + intel_connector->base.name, >> + intel_dp->link_rate, intel_dp->lane_count); >> + if (!intel_dp_get_link_train_fallback_values(intel_dp, >> + intel_dp->link_rate, >> + intel_dp->lane_count)) >> + /* Schedule a Hotplug Uevent to userspace to start modeset */ >> + schedule_work(&intel_connector->modeset_retry_work); >> return; >> } >> -- >> 2.17.0 >> -- Jani Nikula, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
