drm/i915/dp_mst: Simplify computing the min/max compressed bpp limits

Adjusting the compressed bpp range min/max limits in
intel_dp_dsc_nearest_valid_bpp() is unnecessary:

- The source/sink min/max values are enforced already by the
  link_config_limits::min_bpp_x16/max_bpp_x16 values computed early in
  intel_dp_compute_config_link_bpp_limits().
- The fixed set of valid bpps are enforced already - for all bpps in the
  min .. max range by intel_dp_dsc_valid_compressed_bpp() called from
  intel_dp_mtp_tu_compute_config().

The only thing needed is limiting max compressed bpp below the
uncompressed pipe bpp, do that one thing only instead of calling
intel_dp_dsc_nearest_valid_bpp().

Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://lore.kernel.org/r/20250509180340.554867-7-imre.deak@intel.com

1 files changed, 1 insertions, 5 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index ff88888e4b29..42351229177d 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -491,11 +491,7 @@ static int mst_stream_dsc_compute_link_config(struct intel_dp *intel_dp,
 	drm_dbg_kms(display->drm, "DSC Sink supported compressed min bpp %d compressed max bpp %d\n",
 		    min_compressed_bpp, max_compressed_bpp);
 
-	/* Align compressed bpps according to our own constraints */
-	max_compressed_bpp = intel_dp_dsc_nearest_valid_bpp(display, max_compressed_bpp,
-							    crtc_state->pipe_bpp);
-	min_compressed_bpp = intel_dp_dsc_nearest_valid_bpp(display, min_compressed_bpp,
-							    crtc_state->pipe_bpp);
+	max_compressed_bpp = min(max_compressed_bpp, crtc_state->pipe_bpp - 1);
 
 	crtc_state->lane_count = limits->max_lane_count;
 	crtc_state->port_clock = limits->max_rate;