drm/i915: Extract intel_dp_joiner_needs_dsc()

Pull the "does joiner need DSC?" check into a helper. MST will
want to use this too at some point.
Tested-by: Vidya Srinivas <vidya.srinivas@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240404213441.17637-9-ville.syrjala@linux.intel.com

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

@@ -1310,11 +1310,7 @@ intel_dp_mode_valid(struct drm_connector *_connector,
 		dsc = dsc_max_compressed_bpp && dsc_slice_count;
 	}
 
-	/*
-	 * Big joiner configuration needs DSC for TGL which is not true for
-	 * XE_LPD where uncompressed joiner is supported.
-	 */
-	if (DISPLAY_VER(dev_priv) < 13 && bigjoiner && !dsc)
+	if (intel_dp_joiner_needs_dsc(dev_priv, bigjoiner) && !dsc)
 		return MODE_CLOCK_HIGH;
 
 	if (mode_rate > max_rate && !dsc)
@@ -2405,6 +2401,16 @@ int intel_dp_config_required_rate(const struct intel_crtc_state *crtc_state)
 	return intel_dp_link_required(adjusted_mode->crtc_clock, bpp);
 }
 
+bool intel_dp_joiner_needs_dsc(struct drm_i915_private *i915, bool use_joiner)
+{
+	/*
+	 * Pipe joiner needs compression up to display 12 due to bandwidth
+	 * limitation. DG2 onwards pipe joiner can be enabled without
+	 * compression.
+	 */
+	return DISPLAY_VER(i915) < 13 && use_joiner;
+}
+
 static int
 intel_dp_compute_link_config(struct intel_encoder *encoder,
 			     struct intel_crtc_state *pipe_config,
@@ -2419,8 +2425,7 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
 		&pipe_config->hw.adjusted_mode;
 	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
 	struct link_config_limits limits;
-	bool joiner_needs_dsc = false;
-	bool dsc_needed;
+	bool dsc_needed, joiner_needs_dsc;
 	int ret = 0;
 
 	if (pipe_config->fec_enable &&
@@ -2431,12 +2436,7 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
 				    adjusted_mode->crtc_clock))
 		pipe_config->bigjoiner_pipes = GENMASK(crtc->pipe + 1, crtc->pipe);
 
-	/*
-	 * Pipe joiner needs compression up to display 12 due to bandwidth
-	 * limitation. DG2 onwards pipe joiner can be enabled without
-	 * compression.
-	 */
-	joiner_needs_dsc = DISPLAY_VER(i915) < 13 && pipe_config->bigjoiner_pipes;
+	joiner_needs_dsc = intel_dp_joiner_needs_dsc(i915, pipe_config->bigjoiner_pipes);
 
 	dsc_needed = joiner_needs_dsc || intel_dp->force_dsc_en ||
 		     !intel_dp_compute_config_limits(intel_dp, pipe_config,

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

@@ -120,6 +120,7 @@ int intel_dp_effective_data_rate(int pixel_clock, int bpp_x16,
 				 int bw_overhead);
 int intel_dp_max_link_data_rate(struct intel_dp *intel_dp,
 				int max_dprx_rate, int max_dprx_lanes);
+bool intel_dp_joiner_needs_dsc(struct drm_i915_private *i915, bool use_joiner);
 bool intel_dp_has_bigjoiner(struct intel_dp *intel_dp);
 bool intel_dp_needs_vsc_sdp(const struct intel_crtc_state *crtc_state,
 			    const struct drm_connector_state *conn_state);

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

@@ -1377,11 +1377,7 @@ intel_dp_mst_mode_valid_ctx(struct drm_connector *connector,
 		dsc = dsc_max_compressed_bpp && dsc_slice_count;
 	}
 
-	/*
-	 * Big joiner configuration needs DSC for TGL which is not true for
-	 * XE_LPD where uncompressed joiner is supported.
-	 */
-	if (DISPLAY_VER(dev_priv) < 13 && bigjoiner && !dsc) {
+	if (intel_dp_joiner_needs_dsc(dev_priv, bigjoiner) && !dsc) {
 		*status = MODE_CLOCK_HIGH;
 		return 0;
 	}