drm/i915/dsc: Expose dsc sink max slice count via debugfs

Number of DSC slices can be shown in the DSC debugfs so that
test can take a call whether the configuration can support forcing
bigjoiner/ultrajoiner.

v2: used intel_dp_is_edp() as the parameter to
    drm_dp_dsc_sink_max_slice_count() (Jani N)

Reviewed-by: Nemesa Garg <nemesa.garg@intel.com> (v1)
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/3387
Signed-off-by: Swati Sharma <swati2.sharma@intel.com>
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241213093008.2149452-1-swati2.sharma@intel.com

Author: swatish2-linux

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

@@ -1015,6 +1015,8 @@ static int i915_dsc_fec_support_show(struct seq_file *m, void *data)
 								      DP_DSC_YCbCr444)));
 		seq_printf(m, "DSC_Sink_BPP_Precision: %d\n",
 			   drm_dp_dsc_sink_bpp_incr(connector->dp.dsc_dpcd));
+		seq_printf(m, "DSC_Sink_Max_Slice_Count: %d\n",
+			   drm_dp_dsc_sink_max_slice_count((connector->dp.dsc_dpcd), intel_dp_is_edp(intel_dp)));
 		seq_printf(m, "Force_DSC_Enable: %s\n",
 			   str_yes_no(intel_dp->force_dsc_en));
 		if (!intel_dp_is_edp(intel_dp))