drm/i915/dp: Introduce helper to check pixel rate against dotclock limits

Add intel_dp_dotclk_valid() helper, that checks the required pixel rate
against platform dotclock limit. With joined pipes the effective dotclock
limit depends upon the number of joined pipes.

Call the helper from the mode_valid phase and from the compute_config
phase where we need to check the limits for the given target clock for a
given joiner candidate.

v2: Rename the helper to intel_dp_dotclk_valid(). (Imre)

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patch.msgid.link/20260202103731.357416-13-ankit.k.nautiyal@intel.com

3 files changed, 35 insertions, 18 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 6a4edf1538a6..95992172b780 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -1412,6 +1412,18 @@ bool intel_dp_can_join(struct intel_display *display,
 	}
 }
 
+bool intel_dp_dotclk_valid(struct intel_display *display,
+			   int target_clock,
+			   int num_joined_pipes)
+{
+	int max_dotclk = display->cdclk.max_dotclk_freq;
+	int effective_dotclk_limit;
+
+	effective_dotclk_limit = max_dotclk * num_joined_pipes;
+
+	return target_clock <= effective_dotclk_limit;
+}
+
 static enum drm_mode_status
 intel_dp_mode_valid(struct drm_connector *_connector,
 		    const struct drm_display_mode *mode)
@@ -1474,8 +1486,6 @@ intel_dp_mode_valid(struct drm_connector *_connector,
 	 */
 	status = MODE_CLOCK_HIGH;
 	for (num_joined_pipes = 1; num_joined_pipes <= I915_MAX_PIPES; num_joined_pipes++) {
-		int max_dotclk = display->cdclk.max_dotclk_freq;
-
 		if (connector->force_joined_pipes &&
 		    num_joined_pipes != connector->force_joined_pipes)
 			continue;
@@ -1543,9 +1553,9 @@ intel_dp_mode_valid(struct drm_connector *_connector,
 		if (status != MODE_OK)
 			continue;
 
-		max_dotclk *= num_joined_pipes;
-
-		if (target_clock > max_dotclk) {
+		if (!intel_dp_dotclk_valid(display,
+					   target_clock,
+					   num_joined_pipes)) {
 			status = MODE_CLOCK_HIGH;
 			continue;
 		}
@@ -2776,12 +2786,10 @@ intel_dp_compute_link_for_joined_pipes(struct intel_encoder *encoder,
 	const struct drm_display_mode *adjusted_mode =
 		&pipe_config->hw.adjusted_mode;
 	struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
-	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 ||
@@ -2805,7 +2813,10 @@ intel_dp_compute_link_for_joined_pipes(struct intel_encoder *encoder,
 							     fxp_q4_from_int(pipe_config->pipe_bpp),
 							     0, false);
 
-		if (ret || adjusted_mode->crtc_clock > max_dotclk)
+		if (ret ||
+		    !intel_dp_dotclk_valid(display,
+					   adjusted_mode->crtc_clock,
+					   num_joined_pipes))
 			dsc_needed = true;
 	}
 
@@ -2831,7 +2842,9 @@ intel_dp_compute_link_for_joined_pipes(struct intel_encoder *encoder,
 		if (ret < 0)
 			return ret;
 
-		if (adjusted_mode->crtc_clock > max_dotclk)
+		if (!intel_dp_dotclk_valid(display,
+					   adjusted_mode->crtc_clock,
+					   num_joined_pipes))
 			return -EINVAL;
 	}
 
diff --git a/drivers/gpu/drm/i915/display/intel_dp.h b/drivers/gpu/drm/i915/display/intel_dp.h
index ebaa35d23c9c..edeb09372d1e 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.h
+++ b/drivers/gpu/drm/i915/display/intel_dp.h
@@ -224,5 +224,8 @@ int intel_dp_sdp_min_guardband(const struct intel_crtc_state *crtc_state,
 int intel_dp_max_hdisplay_per_pipe(struct intel_display *display);
 bool intel_dp_can_join(struct intel_display *display,
 		       int num_joined_pipes);
+bool intel_dp_dotclk_valid(struct intel_display *display,
+			   int target_clock,
+			   int num_joined_pipes);
 
 #endif /* __INTEL_DP_H__ */
diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
index 634720fec612..83fe389ea2dc 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
@@ -606,12 +606,10 @@ static int mst_stream_compute_link_for_joined_pipes(struct intel_encoder *encode
 		&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 ||
@@ -625,7 +623,10 @@ static int mst_stream_compute_link_for_joined_pipes(struct intel_encoder *encode
 		if (ret == -EDEADLK)
 			return ret;
 
-		if (ret || adjusted_mode->clock > max_dotclk)
+		if (ret ||
+		    !intel_dp_dotclk_valid(display,
+					   adjusted_mode->clock,
+					   num_joined_pipes))
 			dsc_needed = true;
 	}
 
@@ -669,7 +670,9 @@ static int mst_stream_compute_link_for_joined_pipes(struct intel_encoder *encode
 		if (ret)
 			return ret;
 
-		if (adjusted_mode->clock > max_dotclk)
+		if (!intel_dp_dotclk_valid(display,
+					   adjusted_mode->clock,
+					   num_joined_pipes))
 			return -EINVAL;
 	}
 
@@ -1525,8 +1528,6 @@ mst_connector_mode_valid_ctx(struct drm_connector *_connector,
 
 	*status = MODE_CLOCK_HIGH;
 	for (num_joined_pipes = 1; num_joined_pipes <= I915_MAX_PIPES; num_joined_pipes++) {
-		int max_dotclk = display->cdclk.max_dotclk_freq;
-
 		if (connector->force_joined_pipes &&
 		    num_joined_pipes != connector->force_joined_pipes)
 			continue;
@@ -1571,9 +1572,9 @@ mst_connector_mode_valid_ctx(struct drm_connector *_connector,
 		if (*status != MODE_OK)
 			continue;
 
-		max_dotclk *= num_joined_pipes;
-
-		if (mode->clock > max_dotclk) {
+		if (!intel_dp_dotclk_valid(display,
+					   mode->clock,
+					   num_joined_pipes)) {
 			*status = MODE_CLOCK_HIGH;
 			continue;
 		}