3 files changed, 44 insertions, 10 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index d58acc36e3be..e7502a824047 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -355,6 +355,9 @@ int intel_dp_max_lane_count(struct intel_dp *intel_dp)
 /*
  * The required data bandwidth for a mode with given pixel clock and bpp. This
  * is the required net bandwidth independent of the data bandwidth efficiency.
+ *
+ * TODO: check if callers of this functions should use
+ * intel_dp_effective_data_rate() instead.
  */
 int
 intel_dp_link_required(int pixel_clock, int bpp)
@@ -363,6 +366,22 @@ intel_dp_link_required(int pixel_clock, int bpp)
 	return DIV_ROUND_UP(pixel_clock * bpp, 8);
 }
 
+/**
+ * intel_dp_effective_data_rate - Return the pixel data rate accounting for BW allocation overhead
+ * @pixel_clock: pixel clock in kHz
+ * @bpp_x16: bits per pixel .4 fixed point format
+ * @bw_overhead: BW allocation overhead in 1ppm units
+ *
+ * Return the effective pixel data rate in kB/sec units taking into account
+ * the provided SSC, FEC, DSC BW allocation overhead.
+ */
+int intel_dp_effective_data_rate(int pixel_clock, int bpp_x16,
+				 int bw_overhead)
+{
+	return DIV_ROUND_UP_ULL(mul_u32_u32(pixel_clock * bpp_x16, bw_overhead),
+				1000000 * 16 * 8);
+}
+
 /*
  * Given a link rate and lanes, get the data bandwidth.
  *
diff --git a/drivers/gpu/drm/i915/display/intel_dp.h b/drivers/gpu/drm/i915/display/intel_dp.h
index 777aa858f899..05db46b111f2 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.h
+++ b/drivers/gpu/drm/i915/display/intel_dp.h
@@ -103,6 +103,8 @@ bool intel_dp_source_supports_tps4(struct drm_i915_private *i915);
 
 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,
diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index a5ddd1781969..d3d53e1b4489 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -115,6 +115,7 @@ static void intel_dp_mst_compute_m_n(const struct intel_crtc_state *crtc_state,
 	const struct drm_display_mode *adjusted_mode =
 		&crtc_state->hw.adjusted_mode;
 
+	/* TODO: Check WA 14013163432 to set data M/N for full BW utilization. */
 	intel_link_compute_m_n(bpp_x16, crtc_state->lane_count,
 			       adjusted_mode->crtc_clock,
 			       crtc_state->port_clock,
@@ -124,6 +125,18 @@ static void intel_dp_mst_compute_m_n(const struct intel_crtc_state *crtc_state,
 	m_n->tu = DIV_ROUND_UP_ULL(mul_u32_u32(m_n->data_m, 64), m_n->data_n);
 }
 
+static int intel_dp_mst_calc_pbn(int pixel_clock, int bpp_x16, int bw_overhead)
+{
+	int effective_data_rate =
+		intel_dp_effective_data_rate(pixel_clock, bpp_x16, bw_overhead);
+
+	/*
+	 * TODO: Use drm_dp_calc_pbn_mode() instead, once it's converted
+	 * to calculate PBN with the BW overhead passed to it.
+	 */
+	return DIV_ROUND_UP(effective_data_rate * 64, 54 * 1000);
+}
+
 static int intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
 						struct intel_crtc_state *crtc_state,
 						int max_bpp,
@@ -167,10 +180,10 @@ static int intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
 		    min_bpp, max_bpp);
 
 	for (bpp = max_bpp; bpp >= min_bpp; bpp -= step) {
-		struct intel_link_m_n remote_m_n;
 		int local_bw_overhead;
 		int remote_bw_overhead;
 		int link_bpp_x16;
+		int remote_tu;
 
 		drm_dbg_kms(&i915->drm, "Trying bpp %d\n", bpp);
 
@@ -191,11 +204,6 @@ static int intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
 					 link_bpp_x16,
 					 &crtc_state->dp_m_n);
 
-		intel_dp_mst_compute_m_n(crtc_state, connector,
-					 remote_bw_overhead,
-					 link_bpp_x16,
-					 &remote_m_n);
-
 		/*
 		 * The TU size programmed to the HW determines which slots in
 		 * an MTP frame are used for this stream, which needs to match
@@ -210,9 +218,14 @@ static int intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
 		 * crtc_state->dp_m_n.tu), provided that the driver doesn't
 		 * enable SSC on the corresponding link.
 		 */
-		drm_WARN_ON(&i915->drm, remote_m_n.tu < crtc_state->dp_m_n.tu);
-		crtc_state->dp_m_n.tu = remote_m_n.tu;
-		crtc_state->pbn = remote_m_n.tu * dfixed_trunc(mst_state->pbn_div);
+		crtc_state->pbn = intel_dp_mst_calc_pbn(adjusted_mode->crtc_clock,
+							link_bpp_x16,
+							remote_bw_overhead);
+
+		remote_tu = DIV_ROUND_UP(dfixed_const(crtc_state->pbn), mst_state->pbn_div.full);
+
+		drm_WARN_ON(&i915->drm, remote_tu < crtc_state->dp_m_n.tu);
+		crtc_state->dp_m_n.tu = remote_tu;
 
 		slots = drm_dp_atomic_find_time_slots(state, &intel_dp->mst_mgr,
 						      connector->port,
@@ -221,7 +234,7 @@ static int intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
 			return slots;
 
 		if (slots >= 0) {
-			drm_WARN_ON(&i915->drm, slots != remote_m_n.tu);
+			drm_WARN_ON(&i915->drm, slots != crtc_state->dp_m_n.tu);
 
 			break;
 		}