[Intel-gfx] [PATCH] drm/i915: Clean up HDMI deep color handling a bit

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

Reogranize the HDMI deep color state computation to just
loop over possible bpc values. Avoids having to maintain
so many variants of the clock etc.

The current code also looks confused w.r.t. port_clock vs.
bw_constrained. It would happily update port_clock for
deep color but then not actually enable deep color due to
bw_constrained being set. The new logic handles that case
correctly.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/display/intel_hdmi.c | 82 ++++++++++-------------
 1 file changed, 37 insertions(+), 45 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
index e02f0faecf02..ed1a7afc1ffd 100644
--- a/drivers/gpu/drm/i915/display/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
@@ -2262,8 +2262,7 @@ static bool hdmi_deep_color_possible(const struct intel_crtc_state *crtc_state,
 static bool
 intel_hdmi_ycbcr420_config(struct drm_connector *connector,
 			   struct intel_crtc_state *config,
-			   int *clock_12bpc, int *clock_10bpc,
-			   int *clock_8bpc)
+			   int *clock)
 {
 	struct intel_crtc *intel_crtc = to_intel_crtc(config->base.crtc);
 
@@ -2273,10 +2272,7 @@ intel_hdmi_ycbcr420_config(struct drm_connector *connector,
 	}
 
 	/* YCBCR420 TMDS rate requirement is half the pixel clock */
-	config->port_clock /= 2;
-	*clock_12bpc /= 2;
-	*clock_10bpc /= 2;
-	*clock_8bpc /= 2;
+	*clock /= 2;
 	config->output_format = INTEL_OUTPUT_FORMAT_YCBCR420;
 
 	/* YCBCR 420 output conversion needs a scaler */
@@ -2302,10 +2298,7 @@ int intel_hdmi_compute_config(struct intel_encoder *encoder,
 	struct drm_scdc *scdc = &connector->display_info.hdmi.scdc;
 	struct intel_digital_connector_state *intel_conn_state =
 		to_intel_digital_connector_state(conn_state);
-	int clock_8bpc = pipe_config->base.adjusted_mode.crtc_clock;
-	int clock_10bpc = clock_8bpc * 5 / 4;
-	int clock_12bpc = clock_8bpc * 3 / 2;
-	int desired_bpp;
+	int bpc, clock = pipe_config->base.adjusted_mode.crtc_clock;
 	bool force_dvi = intel_conn_state->force_audio == HDMI_AUDIO_OFF_DVI;
 
 	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLSCAN)
@@ -2330,15 +2323,11 @@ int intel_hdmi_compute_config(struct intel_encoder *encoder,
 
 	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK) {
 		pipe_config->pixel_multiplier = 2;
-		clock_8bpc *= 2;
-		clock_10bpc *= 2;
-		clock_12bpc *= 2;
+		clock *= 2;
 	}
 
 	if (drm_mode_is_420_only(&connector->display_info, adjusted_mode)) {
-		if (!intel_hdmi_ycbcr420_config(connector, pipe_config,
-						&clock_12bpc, &clock_10bpc,
-						&clock_8bpc)) {
+		if (!intel_hdmi_ycbcr420_config(connector, pipe_config, &clock)) {
 			DRM_ERROR("Can't support YCBCR420 output\n");
 			return -EINVAL;
 		}
@@ -2355,41 +2344,44 @@ int intel_hdmi_compute_config(struct intel_encoder *encoder,
 				intel_conn_state->force_audio == HDMI_AUDIO_ON;
 	}
 
-	/*
-	 * Note that g4x/vlv don't support 12bpc hdmi outputs. We also need
-	 * to check that the higher clock still fits within limits.
-	 */
-	if (hdmi_deep_color_possible(pipe_config, 12) &&
-	    hdmi_port_clock_valid(intel_hdmi, clock_12bpc,
-				  true, force_dvi) == MODE_OK) {
-		DRM_DEBUG_KMS("picking bpc to 12 for HDMI output\n");
-		desired_bpp = 12*3;
-
-		/* Need to adjust the port link by 1.5x for 12bpc. */
-		pipe_config->port_clock = clock_12bpc;
-	} else if (hdmi_deep_color_possible(pipe_config, 10) &&
-		   hdmi_port_clock_valid(intel_hdmi, clock_10bpc,
-					 true, force_dvi) == MODE_OK) {
-		DRM_DEBUG_KMS("picking bpc to 10 for HDMI output\n");
-		desired_bpp = 10 * 3;
-
-		/* Need to adjust the port link by 1.25x for 10bpc. */
-		pipe_config->port_clock = clock_10bpc;
-	} else {
-		DRM_DEBUG_KMS("picking bpc to 8 for HDMI output\n");
-		desired_bpp = 8*3;
+	/* for 8bpc */
+	pipe_config->port_clock = clock;
 
-		pipe_config->port_clock = clock_8bpc;
-	}
+	for (bpc = 12; bpc > 8; bpc -= 2) {
+		int port_clock;
+
+		if (!hdmi_deep_color_possible(pipe_config, bpc))
+			continue;
+
+		/*
+		 * Need to adjust the port link by:
+		 *  1.5x for 12bpc
+		 *  1.25x for 10bpc
+		 */
+		port_clock = clock * bpc / 8;
+
+		if (hdmi_port_clock_valid(intel_hdmi, port_clock,
+					  true, force_dvi) != MODE_OK)
+			continue;
 
-	if (!pipe_config->bw_constrained) {
-		DRM_DEBUG_KMS("forcing pipe bpp to %i for HDMI\n", desired_bpp);
-		pipe_config->pipe_bpp = desired_bpp;
+		pipe_config->port_clock = port_clock;
+		break;
 	}
 
+	/*
+	 * pipe_bpp could already be below 8bpc due to
+	 * FDI bandwidth constraints. We shouldn't bump it
+	 * back up to 8bpc in that case.
+	 */
+	if (pipe_config->pipe_bpp > bpc * 3)
+		pipe_config->pipe_bpp = bpc * 3;
+	DRM_DEBUG_KMS("picking %dbpc for HDMI output (pipe bpp: %d)\n",
+		      bpc, pipe_config->pipe_bpp);
+
 	if (hdmi_port_clock_valid(intel_hdmi, pipe_config->port_clock,
 				  false, force_dvi) != MODE_OK) {
-		DRM_DEBUG_KMS("unsupported HDMI clock, rejecting mode\n");
+		DRM_DEBUG_KMS("unsupported HDMI clock (%d kHz), rejecting mode\n",
+			      pipe_config->port_clock);
 		return -EINVAL;
 	}
 
-- 
2.21.0