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>

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index ab415f41924d7d1a615ae19d19c11c750f94e27b..5045c34a16be1c6f2879112b5fc91878491a8f6c 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -2356,6 +2356,9 @@ 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);