drm/i915/bigjoiner: Avoid dsc_compute_config for uncompressed bigjoiner

For uncompressed big joiner DSC engine will not be used so will avoid
compute config of DSC.

Cc: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: NAnimesh Manna <animesh.manna@intel.com>
Signed-off-by: NClinton Taylor <Clinton.A.Taylor@intel.com>
Signed-off-by: NMatt Roper <matthew.d.roper@intel.com>
Reviewed-by: NManasi Navare <manasi.d.navare@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210514153711.2359617-15-matthew.d.roper@intel.com

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

@@ -1370,9 +1370,13 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
 	 */
 	ret = intel_dp_compute_link_config_wide(intel_dp, pipe_config, &limits);
 
-	/* enable compression if the mode doesn't fit available BW */
+	/*
+	 * Pipe joiner needs compression upto display12 due to BW limitation. DG2
+	 * onwards pipe joiner can be enabled without compression.
+	 */
 	drm_dbg_kms(&i915->drm, "Force DSC en = %d\n", intel_dp->force_dsc_en);
-	if (ret || intel_dp->force_dsc_en || pipe_config->bigjoiner) {
+	if (ret || intel_dp->force_dsc_en || (DISPLAY_VER(i915) < 13 &&
+					      pipe_config->bigjoiner)) {
 		ret = intel_dp_dsc_compute_config(intel_dp, pipe_config,
 						  conn_state, &limits);
 		if (ret < 0)