drm/i915/dp: Limit SST link rate to <=8.1Gbps

Limit the link rate to HBR3 or below (<=8.1Gbps) in SST mode.
UHBR (10Gbps+) link rates require 128b/132b channel encoding
which we have not yet hooked up into the SST/no-sideband codepaths.

Cc: stable@vger.kernel.org
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240208154552.14545-1-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
(cherry picked from commit 6061811d72e14f41f71b6a025510920b187bfcca)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index f5ef95da55346ff14cc6b102c27e78e8960cec65..ae647d03af25cd48a3151b362c5ed1e752bdba60 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -2355,6 +2355,9 @@ intel_dp_compute_config_limits(struct intel_dp *intel_dp,
        limits->min_rate = intel_dp_common_rate(intel_dp, 0);
        limits->max_rate = intel_dp_max_link_rate(intel_dp);
 
+       /* FIXME 128b/132b SST support missing */
+       limits->max_rate = min(limits->max_rate, 810000);
+
        limits->min_lane_count = 1;
        limits->max_lane_count = intel_dp_max_lane_count(intel_dp);