drm/i915/dp: Limit the output link bpp in DSC mode

Limit the output link bpp in DSC mode to the link_config_limits
link.min_bpp_x16 .. max_bpp_x16 range the same way it's done in non-DSC
mode.  Atm this doesn't make a difference, the link bpp range being
0 .. max pipe bpp, but a follow-up patch will need a way to reduce max
link bpp below its current value.

v2:
- Add to_bpp_int_roundup() instead of open coding it. (Jani)

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230921195159.2646027-6-imre.deak@intel.com

drivers/gpu/drm/i915/display/intel_display_types.h

@@ -2128,6 +2128,11 @@ static inline int to_bpp_frac(int bpp_x16)
 #define BPP_X16_FMT		"%d.%04d"
 #define BPP_X16_ARGS(bpp_x16)	to_bpp_int(bpp_x16), (to_bpp_frac(bpp_x16) * 625)
 
+static inline int to_bpp_int_roundup(int bpp_x16)
+{
+	return (bpp_x16 + 0xf) >> 4;
+}
+
 static inline int to_bpp_x16(int bpp)
 {
 	return bpp << 4;

drivers/gpu/drm/i915/display/intel_dp.c

@@ -1925,6 +1925,7 @@ static int dsc_compute_compressed_bpp(struct intel_dp *intel_dp,
 	dsc_src_min_bpp = dsc_src_min_compressed_bpp();
 	dsc_sink_min_bpp = dsc_sink_min_compressed_bpp(pipe_config);
 	dsc_min_bpp = max(dsc_src_min_bpp, dsc_sink_min_bpp);
+	dsc_min_bpp = max(dsc_min_bpp, to_bpp_int_roundup(limits->link.min_bpp_x16));
 
 	dsc_src_max_bpp = dsc_src_max_compressed_bpp(intel_dp);
 	dsc_sink_max_bpp = dsc_sink_max_compressed_bpp(intel_dp, pipe_config, pipe_bpp / 3);
@@ -1934,6 +1935,7 @@ static int dsc_compute_compressed_bpp(struct intel_dp *intel_dp,
 								adjusted_mode->hdisplay,
 								pipe_config->bigjoiner_pipes);
 	dsc_max_bpp = min(dsc_max_bpp, dsc_joiner_max_bpp);
+	dsc_max_bpp = min(dsc_max_bpp, to_bpp_int(limits->link.max_bpp_x16));
 
 	if (DISPLAY_VER(i915) >= 13)
 		return xelpd_dsc_compute_link_config(intel_dp, pipe_config, limits,
@@ -2079,10 +2081,12 @@ static int intel_edp_dsc_compute_pipe_bpp(struct intel_dp *intel_dp,
 	dsc_src_min_bpp = dsc_src_min_compressed_bpp();
 	dsc_sink_min_bpp = dsc_sink_min_compressed_bpp(pipe_config);
 	dsc_min_bpp = max(dsc_src_min_bpp, dsc_sink_min_bpp);
+	dsc_min_bpp = max(dsc_min_bpp, to_bpp_int_roundup(limits->link.min_bpp_x16));
 
 	dsc_src_max_bpp = dsc_src_max_compressed_bpp(intel_dp);
 	dsc_sink_max_bpp = dsc_sink_max_compressed_bpp(intel_dp, pipe_config, pipe_bpp / 3);
 	dsc_max_bpp = dsc_sink_max_bpp ? min(dsc_sink_max_bpp, dsc_src_max_bpp) : dsc_src_max_bpp;
+	dsc_max_bpp = min(dsc_max_bpp, to_bpp_int(limits->link.max_bpp_x16));
 
 	/* Compressed BPP should be less than the Input DSC bpp */
 	dsc_max_bpp = min(dsc_max_bpp, pipe_bpp - 1);

drivers/gpu/drm/i915/display/intel_dp_mst.c

@@ -233,6 +233,9 @@ static int intel_dp_dsc_mst_compute_link_config(struct intel_encoder *encoder,
 	if (max_bpp > sink_max_bpp)
 		max_bpp = sink_max_bpp;
 
+	min_bpp = max(min_bpp, to_bpp_int_roundup(limits->link.min_bpp_x16));
+	max_bpp = min(max_bpp, to_bpp_int(limits->link.max_bpp_x16));
+
 	slots = intel_dp_mst_find_vcpi_slots_for_bpp(encoder, crtc_state, max_bpp,
 						     min_bpp, limits,
 						     conn_state, 2 * 3, true);