drm/i915/dp: Use drm_dp_max_dprx_data_rate()

Instead of intel_dp_max_data_rate() use the equivalent
drm_dp_max_dprx_data_rate() which was copied from the former one in a
previous patch.
Reviewed-by: Uma Shankar <uma.shankar@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/20240220211841.448846-6-imre.deak@intel.com

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

@@ -2478,7 +2478,7 @@ intel_link_compute_m_n(u16 bits_per_pixel_x16, int nlanes,
 	u32 link_symbol_clock = intel_dp_link_symbol_clock(link_clock);
 	u32 data_m = intel_dp_effective_data_rate(pixel_clock, bits_per_pixel_x16,
 						  bw_overhead);
-	u32 data_n = intel_dp_max_data_rate(link_clock, nlanes);
+	u32 data_n = drm_dp_max_dprx_data_rate(link_clock, nlanes);
 
 	/*
 	 * Windows/BIOS uses fixed M/N values always. Follow suit.

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

@@ -383,52 +383,6 @@ int intel_dp_effective_data_rate(int pixel_clock, int bpp_x16,
 				1000000 * 16 * 8);
 }
 
-/*
- * Given a link rate and lanes, get the data bandwidth.
- *
- * Data bandwidth is the actual payload rate, which depends on the data
- * bandwidth efficiency and the link rate.
- *
- * For 8b/10b channel encoding, SST and non-FEC, the data bandwidth efficiency
- * is 80%. For example, for a 1.62 Gbps link, 1.62*10^9 bps * 0.80 * (1/8) =
- * 162000 kBps. With 8-bit symbols, we have 162000 kHz symbol clock. Just by
- * coincidence, the port clock in kHz matches the data bandwidth in kBps, and
- * they equal the link bit rate in Gbps multiplied by 100000. (Note that this no
- * longer holds for data bandwidth as soon as FEC or MST is taken into account!)
- *
- * For 128b/132b channel encoding, the data bandwidth efficiency is 96.71%. For
- * example, for a 10 Gbps link, 10*10^9 bps * 0.9671 * (1/8) = 1208875
- * kBps. With 32-bit symbols, we have 312500 kHz symbol clock. The value 1000000
- * does not match the symbol clock, the port clock (not even if you think in
- * terms of a byte clock), nor the data bandwidth. It only matches the link bit
- * rate in units of 10000 bps.
- */
-int
-intel_dp_max_data_rate(int max_link_rate, int max_lanes)
-{
-	int ch_coding_efficiency =
-		drm_dp_bw_channel_coding_efficiency(drm_dp_is_uhbr_rate(max_link_rate));
-	int max_link_rate_kbps = max_link_rate * 10;
-
-	/*
-	 * UHBR rates always use 128b/132b channel encoding, and have
-	 * 97.71% data bandwidth efficiency. Consider max_link_rate the
-	 * link bit rate in units of 10000 bps.
-	 */
-	/*
-	 * Lower than UHBR rates always use 8b/10b channel encoding, and have
-	 * 80% data bandwidth efficiency for SST non-FEC. However, this turns
-	 * out to be a nop by coincidence:
-	 *
-	 *	int max_link_rate_kbps = max_link_rate * 10;
-	 *	max_link_rate_kbps = DIV_ROUND_DOWN_ULL(max_link_rate_kbps * 8, 10);
-	 *	max_link_rate = max_link_rate_kbps / 8;
-	 */
-	return DIV_ROUND_DOWN_ULL(mul_u32_u32(max_link_rate_kbps * max_lanes,
-					      ch_coding_efficiency),
-				  1000000 * 8);
-}
-
 bool intel_dp_can_bigjoiner(struct intel_dp *intel_dp)
 {
 	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
@@ -658,7 +612,7 @@ static bool intel_dp_can_link_train_fallback_for_edp(struct intel_dp *intel_dp,
 	int mode_rate, max_rate;
 
 	mode_rate = intel_dp_link_required(fixed_mode->clock, 18);
-	max_rate = intel_dp_max_data_rate(link_rate, lane_count);
+	max_rate = drm_dp_max_dprx_data_rate(link_rate, lane_count);
 	if (mode_rate > max_rate)
 		return false;
 
@@ -1262,7 +1216,7 @@ intel_dp_mode_valid(struct drm_connector *_connector,
 	max_link_clock = intel_dp_max_link_rate(intel_dp);
 	max_lanes = intel_dp_max_lane_count(intel_dp);
 
-	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
+	max_rate = drm_dp_max_dprx_data_rate(max_link_clock, max_lanes);
 	mode_rate = intel_dp_link_required(target_clock,
 					   intel_dp_mode_min_output_bpp(connector, mode));
 
@@ -1612,7 +1566,7 @@ intel_dp_compute_link_config_wide(struct intel_dp *intel_dp,
 			for (lane_count = limits->min_lane_count;
 			     lane_count <= limits->max_lane_count;
 			     lane_count <<= 1) {
-				link_avail = intel_dp_max_data_rate(link_rate,
+				link_avail = drm_dp_max_dprx_data_rate(link_rate,
 								       lane_count);
 
 				if (mode_rate <= link_avail) {
@@ -2467,7 +2421,7 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
 			    "DP link rate required %i available %i\n",
 			    intel_dp_link_required(adjusted_mode->crtc_clock,
 						   to_bpp_int_roundup(pipe_config->dsc.compressed_bpp_x16)),
-			    intel_dp_max_data_rate(pipe_config->port_clock,
+			    drm_dp_max_dprx_data_rate(pipe_config->port_clock,
 						      pipe_config->lane_count));
 	} else {
 		drm_dbg_kms(&i915->drm, "DP lane count %d clock %d bpp %d\n",
@@ -2478,7 +2432,7 @@ intel_dp_compute_link_config(struct intel_encoder *encoder,
 			    "DP link rate required %i available %i\n",
 			    intel_dp_link_required(adjusted_mode->crtc_clock,
 						   pipe_config->pipe_bpp),
-			    intel_dp_max_data_rate(pipe_config->port_clock,
+			    drm_dp_max_dprx_data_rate(pipe_config->port_clock,
 						      pipe_config->lane_count));
 	}
 	return 0;

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

@@ -111,7 +111,6 @@ bool intel_dp_get_colorimetry_status(struct intel_dp *intel_dp);
 int intel_dp_link_required(int pixel_clock, int bpp);
 int intel_dp_effective_data_rate(int pixel_clock, int bpp_x16,
 				 int bw_overhead);
-int intel_dp_max_data_rate(int max_link_rate, int max_lanes);
 bool intel_dp_can_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

@@ -1299,7 +1299,7 @@ intel_dp_mst_mode_valid_ctx(struct drm_connector *connector,
 	max_link_clock = intel_dp_max_link_rate(intel_dp);
 	max_lanes = intel_dp_max_lane_count(intel_dp);
 
-	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
+	max_rate = drm_dp_max_dprx_data_rate(max_link_clock, max_lanes);
 	mode_rate = intel_dp_link_required(mode->clock, min_bpp);
 
 	ret = drm_modeset_lock(&mgr->base.lock, ctx);