drm/i915/dp_mst: Calculate the BW overhead in intel_dp_mst_find_vcpi_slots_for_bpp()

The next patch will calculate the PBN value directly from the pixel data
rate and the BW allocation overhead, not requiring the data, link M/N
and TU values for this. To prepare for that move the calculation of BW
overheads from intel_dp_mst_compute_m_n() to
intel_dp_mst_find_vcpi_slots_for_bpp().

While at it store link_bpp in a .4 fixed point format.

Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231116131841.1588781-8-imre.deak@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index e5d6b811c22ef4060a7cd6f5189d52083f66ca0c..a5ddd1781969d64acd6293aad7cd021e1ea8022f 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -108,15 +108,12 @@ static int intel_dp_mst_bw_overhead(const struct intel_crtc_state *crtc_state,
 
 static void intel_dp_mst_compute_m_n(const struct intel_crtc_state *crtc_state,
                                     const struct intel_connector *connector,
-                                    bool ssc, bool dsc,
+                                    int overhead,
                                     int bpp_x16,
                                     struct intel_link_m_n *m_n)
 {
        const struct drm_display_mode *adjusted_mode =
                &crtc_state->hw.adjusted_mode;
-       int overhead = intel_dp_mst_bw_overhead(crtc_state,
-                                               connector,
-                                               ssc, dsc, bpp_x16);
 
        intel_link_compute_m_n(bpp_x16, crtc_state->lane_count,
                               adjusted_mode->crtc_clock,
@@ -171,7 +168,9 @@ static int intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
 
        for (bpp = max_bpp; bpp >= min_bpp; bpp -= step) {
                struct intel_link_m_n remote_m_n;
-               int link_bpp;
+               int local_bw_overhead;
+               int remote_bw_overhead;
+               int link_bpp_x16;
 
                drm_dbg_kms(&i915->drm, "Trying bpp %d\n", bpp);
 
@@ -179,12 +178,22 @@ static int intel_dp_mst_find_vcpi_slots_for_bpp(struct intel_encoder *encoder,
                if (ret)
                        continue;
 
-               link_bpp = dsc ? bpp :
-                       intel_dp_output_bpp(crtc_state->output_format, bpp);
+               link_bpp_x16 = to_bpp_x16(dsc ? bpp :
+                                         intel_dp_output_bpp(crtc_state->output_format, bpp));
 
-               intel_dp_mst_compute_m_n(crtc_state, connector, false, dsc, to_bpp_x16(link_bpp),
+               local_bw_overhead = intel_dp_mst_bw_overhead(crtc_state, connector,
+                                                            false, dsc, link_bpp_x16);
+               remote_bw_overhead = intel_dp_mst_bw_overhead(crtc_state, connector,
+                                                             true, dsc, link_bpp_x16);
+
+               intel_dp_mst_compute_m_n(crtc_state, connector,
+                                        local_bw_overhead,
+                                        link_bpp_x16,
                                         &crtc_state->dp_m_n);
-               intel_dp_mst_compute_m_n(crtc_state, connector, true, dsc, to_bpp_x16(link_bpp),
+
+               intel_dp_mst_compute_m_n(crtc_state, connector,
+                                        remote_bw_overhead,
+                                        link_bpp_x16,
                                         &remote_m_n);
 
                /*