drm/i915: convert DP autodither code to new infrastructure

The old code only handled either 6bpc or 8bpc. Since it's easy to do,
reorganize the code to be a bit more generic so that it can also handle
10bpc and 12bpc. Note that we still start with 8bpc, so there's no
functional change.

Also, since we no don't need to compute the 6BPC flag in the mode_valid
callback, we can consolidate things a bit. That requires though that
the link bw computation is moved up in the compute_config callback.
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -7485,10 +7485,6 @@ intel_modeset_pipe_config(struct drm_crtc *crtc,
 		}
 	}
 
-	/* temporary hack until the DP code doesn't use the 6BPC flag any more */
-	if (pipe_config->adjusted_mode.private_flags & INTEL_MODE_DP_FORCE_6BPC)
-		pipe_config->pipe_bpp = 6*8;
-
 	if (!(intel_crtc_compute_config(crtc, pipe_config))) {
 		DRM_DEBUG_KMS("CRTC fixup failed\n");
 		goto fail;

drivers/gpu/drm/i915/intel_dp.c

@@ -177,34 +177,6 @@ intel_dp_max_data_rate(int max_link_clock, int max_lanes)
 	return (max_link_clock * max_lanes * 8) / 10;
 }
 
-static bool
-intel_dp_adjust_dithering(struct intel_dp *intel_dp,
-			  struct drm_display_mode *mode,
-			  bool adjust_mode)
-{
-	int max_link_clock =
-		drm_dp_bw_code_to_link_rate(intel_dp_max_link_bw(intel_dp));
-	int max_lanes = drm_dp_max_lane_count(intel_dp->dpcd);
-	int max_rate, mode_rate;
-
-	mode_rate = intel_dp_link_required(mode->clock, 24);
-	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
-
-	if (mode_rate > max_rate) {
-		mode_rate = intel_dp_link_required(mode->clock, 18);
-		if (mode_rate > max_rate)
-			return false;
-
-		if (adjust_mode)
-			mode->private_flags
-				|= INTEL_MODE_DP_FORCE_6BPC;
-
-		return true;
-	}
-
-	return true;
-}
-
 static int
 intel_dp_mode_valid(struct drm_connector *connector,
 		    struct drm_display_mode *mode)
@@ -212,6 +184,8 @@ intel_dp_mode_valid(struct drm_connector *connector,
 	struct intel_dp *intel_dp = intel_attached_dp(connector);
 	struct intel_connector *intel_connector = to_intel_connector(connector);
 	struct drm_display_mode *fixed_mode = intel_connector->panel.fixed_mode;
+	int target_clock = mode->clock;
+	int max_rate, mode_rate, max_lanes, max_link_clock;
 
 	if (is_edp(intel_dp) && fixed_mode) {
 		if (mode->hdisplay > fixed_mode->hdisplay)
@@ -221,7 +195,13 @@ intel_dp_mode_valid(struct drm_connector *connector,
 			return MODE_PANEL;
 	}
 
-	if (!intel_dp_adjust_dithering(intel_dp, mode, false))
+	max_link_clock = drm_dp_bw_code_to_link_rate(intel_dp_max_link_bw(intel_dp));
+	max_lanes = drm_dp_max_lane_count(intel_dp->dpcd);
+
+	max_rate = intel_dp_max_data_rate(max_link_clock, max_lanes);
+	mode_rate = intel_dp_link_required(target_clock, 18);
+
+	if (mode_rate > max_rate)
 		return MODE_CLOCK_HIGH;
 
 	if (mode->clock < 10000)
@@ -693,6 +673,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 			struct intel_crtc_config *pipe_config)
 {
 	struct drm_device *dev = encoder->base.dev;
+	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct drm_display_mode *adjusted_mode = &pipe_config->adjusted_mode;
 	struct drm_display_mode *mode = &pipe_config->requested_mode;
 	struct intel_dp *intel_dp = enc_to_intel_dp(&encoder->base);
@@ -702,6 +683,7 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 	int max_clock = intel_dp_max_link_bw(intel_dp) == DP_LINK_BW_2_7 ? 1 : 0;
 	int bpp, mode_rate;
 	static int bws[2] = { DP_LINK_BW_1_62, DP_LINK_BW_2_7 };
+	int target_clock, link_avail, link_clock;
 
 	if (HAS_PCH_SPLIT(dev) && !HAS_DDI(dev) && !is_cpu_edp(intel_dp))
 		pipe_config->has_pch_encoder = true;
@@ -713,6 +695,8 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 					intel_connector->panel.fitting_mode,
 					mode, adjusted_mode);
 	}
+	/* We need to take the panel's fixed mode into account. */
+	target_clock = adjusted_mode->clock;
 
 	if (adjusted_mode->flags & DRM_MODE_FLAG_DBLCLK)
 		return false;
@@ -721,11 +705,31 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 		      "max bw %02x pixel clock %iKHz\n",
 		      max_lane_count, bws[max_clock], adjusted_mode->clock);
 
-	if (!intel_dp_adjust_dithering(intel_dp, adjusted_mode, true))
-		return false;
+	/* Walk through all bpp values. Luckily they're all nicely spaced with 2
+	 * bpc in between. */
+	bpp = 8*3;
+	if (is_edp(intel_dp) && dev_priv->edp.bpp)
+		bpp = min_t(int, bpp, dev_priv->edp.bpp);
+
+	for (; bpp >= 6*3; bpp -= 2*3) {
+		mode_rate = intel_dp_link_required(target_clock, bpp);
+
+		for (clock = 0; clock <= max_clock; clock++) {
+			for (lane_count = 1; lane_count <= max_lane_count; lane_count <<= 1) {
+				link_clock = drm_dp_bw_code_to_link_rate(bws[clock]);
+				link_avail = intel_dp_max_data_rate(link_clock,
+								    lane_count);
+
+				if (mode_rate <= link_avail) {
+					goto found;
+				}
+			}
+		}
+	}
 
-	bpp = adjusted_mode->private_flags & INTEL_MODE_DP_FORCE_6BPC ? 18 : 24;
+	return false;
 
+found:
 	if (intel_dp->color_range_auto) {
 		/*
 		 * See:
@@ -741,31 +745,18 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 	if (intel_dp->color_range)
 		pipe_config->limited_color_range = true;
 
-	mode_rate = intel_dp_link_required(adjusted_mode->clock, bpp);
-
-	for (clock = 0; clock <= max_clock; clock++) {
-		for (lane_count = 1; lane_count <= max_lane_count; lane_count <<= 1) {
-			int link_bw_clock =
-				drm_dp_bw_code_to_link_rate(bws[clock]);
-			int link_avail = intel_dp_max_data_rate(link_bw_clock,
-								lane_count);
-
-			if (mode_rate <= link_avail) {
 	intel_dp->link_bw = bws[clock];
 	intel_dp->lane_count = lane_count;
-				adjusted_mode->clock = link_bw_clock;
-				DRM_DEBUG_KMS("DP link bw %02x lane "
-						"count %d clock %d bpp %d\n",
+	adjusted_mode->clock = drm_dp_bw_code_to_link_rate(intel_dp->link_bw);
+	pipe_config->pipe_bpp = bpp;
+
+	DRM_DEBUG_KMS("DP link bw %02x lane count %d clock %d bpp %d\n",
 		      intel_dp->link_bw, intel_dp->lane_count,
 		      adjusted_mode->clock, bpp);
 	DRM_DEBUG_KMS("DP link bw required %i available %i\n",
 		      mode_rate, link_avail);
-				return true;
-			}
-		}
-	}
 
-	return false;
+	return true;
 }
 
 void

drivers/gpu/drm/i915/intel_drv.h

@@ -101,9 +101,6 @@
 #define INTEL_DVO_CHIP_TMDS 2
 #define INTEL_DVO_CHIP_TVOUT 4
 
-/* drm_display_mode->private_flags */
-#define INTEL_MODE_DP_FORCE_6BPC (0x10)
-
 struct intel_framebuffer {
 	struct drm_framebuffer base;
 	struct drm_i915_gem_object *obj;