[PATCH 10/17] 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.

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>
---
 drivers/gpu/drm/i915/display/intel_dp_mst.c | 43 +++++++++++++++------
 1 file changed, 32 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index 9c6b27f35114..634720fec612 100644
--- 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;
 
-- 
2.45.2