drm/i915/dp_mst: Rework pipe joiner logic in compute_config

Similar to the DP SST, refactor mst_stream_compute_config() to iterate
over joiner candidates and select the minimal joiner configuration that
satisfies the mode requirements. This prepares the logic for future changes
that will consider DSC slice overhead.

v2:
 - Move the check for dotclock in the new helper and check for both DSC and
   non-DSC case. In case the check fails for non-DSC, fallback to DSC
   configuration. (Imre)
 - Propagate the return value from the core helper:
   mst_stream_compute_link_for_joined_pipes(). (Imre)
v3:
 - Use num_joined_pipes instead of num_pipes. (Imre)
v4:
 - Switch to 'ret == 0' for break condition to match SST code.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patch.msgid.link/20260202103731.357416-11-ankit.k.nautiyal@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 9c6b27f35114c35e1716e9cb8a1a6e6d9df58362..634720fec612ef5ecbb2b45f433dcc22c3409eb5 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -602,12 +602,16 @@ static int mst_stream_compute_link_for_joined_pipes(struct intel_encoder *encode
 {
        struct intel_display *display = to_intel_display(encoder);
        struct intel_dp *intel_dp = to_primary_dp(encoder);
+       const struct drm_display_mode *adjusted_mode =
+               &pipe_config->hw.adjusted_mode;
        struct intel_connector *connector =
                to_intel_connector(conn_state->connector);
+       int max_dotclk = display->cdclk.max_dotclk_freq;
        struct link_config_limits limits;
        bool dsc_needed, joiner_needs_dsc;
        int ret = 0;
 
+       max_dotclk *= num_joined_pipes;
        joiner_needs_dsc = intel_dp_joiner_needs_dsc(display, num_joined_pipes);
 
        dsc_needed = joiner_needs_dsc || intel_dp->force_dsc_en ||
@@ -621,7 +625,7 @@ static int mst_stream_compute_link_for_joined_pipes(struct intel_encoder *encode
                if (ret == -EDEADLK)
                        return ret;
 
-               if (ret)
+               if (ret || adjusted_mode->clock > max_dotclk)
                        dsc_needed = true;
        }
 
@@ -664,6 +668,9 @@ static int mst_stream_compute_link_for_joined_pipes(struct intel_encoder *encode
                                                  pipe_config->dp_m_n.tu);
                if (ret)
                        return ret;
+
+               if (adjusted_mode->clock > max_dotclk)
+                       return -EINVAL;
        }
 
        if (ret)
@@ -689,7 +696,7 @@ static int mst_stream_compute_config(struct intel_encoder *encoder,
        const struct drm_display_mode *adjusted_mode =
                &pipe_config->hw.adjusted_mode;
        int num_joined_pipes;
-       int ret = 0;
+       int ret = -EINVAL;
 
        if (pipe_config->fec_enable &&
            !intel_dp_supports_fec(intel_dp, connector, pipe_config))
@@ -702,16 +709,30 @@ static int mst_stream_compute_config(struct intel_encoder *encoder,
        pipe_config->output_format = INTEL_OUTPUT_FORMAT_RGB;
        pipe_config->has_pch_encoder = false;
 
-       num_joined_pipes = intel_dp_num_joined_pipes(intel_dp, connector,
-                                                    adjusted_mode->crtc_hdisplay,
-                                                    adjusted_mode->crtc_clock);
-       if (num_joined_pipes > 1)
-               pipe_config->joiner_pipes = GENMASK(crtc->pipe + num_joined_pipes - 1, crtc->pipe);
+       for (num_joined_pipes = 1; num_joined_pipes <= I915_MAX_PIPES; num_joined_pipes++) {
+               if (connector->force_joined_pipes &&
+                   num_joined_pipes != connector->force_joined_pipes)
+                       continue;
+
+               if (!intel_dp_can_join(display, num_joined_pipes))
+                       continue;
+
+               if (adjusted_mode->hdisplay >
+                   num_joined_pipes * intel_dp_max_hdisplay_per_pipe(display))
+                       continue;
+
+               if (num_joined_pipes > 1)
+                       pipe_config->joiner_pipes = GENMASK(crtc->pipe + num_joined_pipes - 1,
+                                                           crtc->pipe);
+
+               ret = mst_stream_compute_link_for_joined_pipes(encoder,
+                                                              pipe_config,
+                                                              conn_state,
+                                                              num_joined_pipes);
+               if (ret == 0)
+                       break;
+       }
 
-       ret = mst_stream_compute_link_for_joined_pipes(encoder,
-                                                      pipe_config,
-                                                      conn_state,
-                                                      num_joined_pipes);
        if (ret)
                return ret;