We do have to continue the investigation on the link training side, but since 76711 is a critical I'm completely in favor of this workaround for now.
I just tested and it worked very well here, so: Tested-by: Rodrigo Vivi <rodrigo.v...@gmail.com> Reviewed-by: Rodrigo Vivi <rodrigo.v...@gmail.com> On Wed, May 14, 2014 at 6:02 AM, Jani Nikula <jani.nik...@intel.com> wrote: > There are certain BDW high res eDP machines that regressed due to > > commit 38aecea0ccbb909d635619cba22f1891e589b434 > Author: Daniel Vetter <daniel.vet...@ffwll.ch> > Date: Mon Mar 3 11:18:10 2014 +0100 > > drm/i915: reverse dp link param selection, prefer fast over wide again > > The commit lead to 2 lanes at 5.4 Gbps being used instead of 4 lanes at > 2.7 Gbps on the affected machines. Link training succeeded for both, but > the screen remained blank with the former config. Further investigation > showed that 4 lanes at 5.4 Gbps worked also. > > The root cause for the blank screen using 2 lanes remains unknown, but > apparently the driver for a certain other operating system by default > uses the max available lanes. Follow suit on Broadwell eDP, for at least > until we figure out what is going on. > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76711 > Reviewed-by: Daniel Vetter <daniel.vet...@ffwll.ch> > Signed-off-by: Jani Nikula <jani.nik...@intel.com> > --- > drivers/gpu/drm/i915/intel_dp.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/intel_dp.c > b/drivers/gpu/drm/i915/intel_dp.c > index 9f67b724dc28..6eaefca0048d 100644 > --- a/drivers/gpu/drm/i915/intel_dp.c > +++ b/drivers/gpu/drm/i915/intel_dp.c > @@ -849,7 +849,12 @@ intel_dp_compute_config(struct intel_encoder *encoder, > bpp = dev_priv->vbt.edp_bpp; > } > > - if (dev_priv->vbt.edp_lanes) { > + if (IS_BROADWELL(dev)) { > + /* Yes, it's an ugly hack. */ > + min_lane_count = max_lane_count; > + DRM_DEBUG_KMS("forcing lane count to max (%u) on > BDW\n", > + min_lane_count); > + } else if (dev_priv->vbt.edp_lanes) { > min_lane_count = min(dev_priv->vbt.edp_lanes, > max_lane_count); > DRM_DEBUG_KMS("using min %u lanes per VBT\n", > -- > 1.9.1 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/intel-gfx > -- Rodrigo Vivi Blog: http://blog.vivi.eng.br
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