From: Ville Syrjälä ville.syrjala@linux.intel.com
commit bb1a71f9c4672fbfcf2158fd57d0c5c0cdae5612 upstream.
My attempt at allowing MST to use the higher color depths has regressed some configurations. Apparently people have setups where all MST streams will fit into the DP link with 8bpc but won't fit with higher color depths.
What we really should be doing is reducing the bpc for all the streams on the same link until they start to fit. But that requires a bit more work, so in the meantime let's revert back closer to the old behavior and limit MST to at most 8bpc.
Cc: stable@vger.kernel.org Cc: Lyude Paul lyude@redhat.com Tested-by: Geoffrey Bennett gmux22@gmail.com Fixes: f1477219869c ("drm/i915: Remove the 8bpc shackles from DP MST") Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111505 Signed-off-by: Ville Syrjälä ville.syrjala@linux.intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20190828102059.2512-1-ville.sy... Reviewed-by: Lyude Paul lyude@redhat.com (cherry picked from commit 75427b2a2bffc083d51dec389c235722a9c69b05) Signed-off-by: Jani Nikula jani.nikula@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/gpu/drm/i915/intel_dp_mst.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
--- a/drivers/gpu/drm/i915/intel_dp_mst.c +++ b/drivers/gpu/drm/i915/intel_dp_mst.c @@ -125,7 +125,15 @@ static int intel_dp_mst_compute_config(s limits.max_lane_count = intel_dp_max_lane_count(intel_dp);
limits.min_bpp = intel_dp_min_bpp(pipe_config); - limits.max_bpp = pipe_config->pipe_bpp; + /* + * FIXME: If all the streams can't fit into the link with + * their current pipe_bpp we should reduce pipe_bpp across + * the board until things start to fit. Until then we + * limit to <= 8bpc since that's what was hardcoded for all + * MST streams previously. This hack should be removed once + * we have the proper retry logic in place. + */ + limits.max_bpp = min(pipe_config->pipe_bpp, 24);
intel_dp_adjust_compliance_config(intel_dp, pipe_config, &limits);