[PATCH 10/16] drm/i915/dp_mst: Rework pipe joiner logic in compute_config

[Ankit Nautiyal <ankit.k.nautiyal@intel.com>]

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.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp_mst.c | 47 +++++++++++++++++----
 1 file changed, 38 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index 29ac7b2e1e9c..7a83af89ef03 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -687,6 +687,7 @@ 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 num_pipes;
 	int ret = 0;
 
 	if (pipe_config->fec_enable &&
@@ -700,17 +701,45 @@ 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);
+	for (num_pipes = 0; num_pipes < I915_MAX_PIPES; num_pipes++) {
+		int max_dotclk = display->cdclk.max_dotclk_freq;
 
-	if (num_joined_pipes > 1)
-		pipe_config->joiner_pipes = GENMASK(crtc->pipe + num_joined_pipes - 1, crtc->pipe);
+		ret = -EINVAL;
+
+		if (num_pipes == 0) {
+			if (!connector->force_joined_pipes)
+				continue;
+			num_joined_pipes = connector->force_joined_pipes;
+		} else {
+			num_joined_pipes = num_pipes;
+		}
+
+		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)
+			continue;
+
+		max_dotclk *= num_joined_pipes;
+
+		if (adjusted_mode->clock <= max_dotclk) {
+			ret = 0;
+			break;
+		}
+	}
 
-	ret = mst_stream_compute_link_for_joined_pipes(encoder,
-						       pipe_config,
-						       conn_state,
-						       num_joined_pipes);
 	if (ret)
 		return ret;
 
-- 
2.45.2