drm/i915/dp: Add a separate function to reduce the link parameters

A follow-up patch will add an alternative way to reduce the link
parameters in BW order on MST links, prepare for that here.

Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240722165503.2084999-8-imre.deak@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
index 58dea87a9fa280b3c2658e1fcde1df6ab7954d93..57536ae200b77bf30ef0f932e21f1d6f9050bb10 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -1193,6 +1193,36 @@ static int reduce_lane_count(struct intel_dp *intel_dp, int current_lane_count)
        return current_lane_count >> 1;
 }
 
+static bool reduce_link_params_in_rate_lane_order(struct intel_dp *intel_dp,
+                                                 const struct intel_crtc_state *crtc_state,
+                                                 int *new_link_rate, int *new_lane_count)
+{
+       int link_rate;
+       int lane_count;
+
+       lane_count = crtc_state->lane_count;
+       link_rate = reduce_link_rate(intel_dp, crtc_state->port_clock);
+       if (link_rate < 0) {
+               lane_count = reduce_lane_count(intel_dp, crtc_state->lane_count);
+               link_rate = intel_dp_max_common_rate(intel_dp);
+       }
+
+       if (lane_count < 0)
+               return false;
+
+       *new_link_rate = link_rate;
+       *new_lane_count = lane_count;
+
+       return true;
+}
+
+static bool reduce_link_params(struct intel_dp *intel_dp, const struct intel_crtc_state *crtc_state,
+                              int *new_link_rate, int *new_lane_count)
+{
+       return reduce_link_params_in_rate_lane_order(intel_dp, crtc_state,
+                                                    new_link_rate, new_lane_count);
+}
+
 static int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
                                                   const struct intel_crtc_state *crtc_state)
 {
@@ -1206,14 +1236,7 @@ static int intel_dp_get_link_train_fallback_values(struct intel_dp *intel_dp,
                return 0;
        }
 
-       new_lane_count = crtc_state->lane_count;
-       new_link_rate = reduce_link_rate(intel_dp, crtc_state->port_clock);
-       if (new_link_rate < 0) {
-               new_lane_count = reduce_lane_count(intel_dp, crtc_state->lane_count);
-               new_link_rate = intel_dp_max_common_rate(intel_dp);
-       }
-
-       if (new_lane_count < 0)
+       if (!reduce_link_params(intel_dp, crtc_state, &new_link_rate, &new_lane_count))
                return -1;
 
        if (intel_dp_is_edp(intel_dp) &&