drm/i915: Add support for limited color range of broadcast outputs

In order to prevent "crushed blacks" on TVs, the range of the RGB output
may be limited to 16-235. This used to be available through Xorg under
the "Broadcast RGB" option, so reintroduce support for KMS.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=34543
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 14 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 7ffb324b6a7d..3216adcf54d2 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -49,6 +49,7 @@ struct intel_dp {
         uint8_t  link_configuration[DP_LINK_CONFIGURATION_SIZE];
         bool has_audio;
         int force_audio;
+        uint32_t color_range;
         int dpms_mode;
         uint8_t link_bw;
         uint8_t lane_count;
@@ -741,8 +742,8 @@ intel_dp_mode_set(struct drm_encoder *encoder, struct drm_display_mode *mode,
         struct drm_crtc *crtc = intel_dp->base.base.crtc;
         struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 
-        intel_dp->DP = (DP_VOLTAGE_0_4 |
-                       DP_PRE_EMPHASIS_0);
+        intel_dp->DP = DP_VOLTAGE_0_4 | DP_PRE_EMPHASIS_0;
+        intel_dp->DP |= intel_dp->color_range;
 
         if (adjusted_mode->flags & DRM_MODE_FLAG_PHSYNC)
                 intel_dp->DP |= DP_SYNC_HS_HIGH;
@@ -1680,6 +1681,7 @@ intel_dp_set_property(struct drm_connector *connector,
                       struct drm_property *property,
                       uint64_t val)
 {
+        struct drm_i915_private *dev_priv = connector->dev->dev_private;
         struct intel_dp *intel_dp = intel_attached_dp(connector);
         int ret;
 
@@ -1708,6 +1710,14 @@ intel_dp_set_property(struct drm_connector *connector,
                 goto done;
         }
 
+        if (property == dev_priv->broadcast_rgb_property) {
+                if (val == !!intel_dp->color_range)
+                        return 0;
+
+                intel_dp->color_range = val ? DP_COLOR_RANGE_16_235 : 0;
+                goto done;
+        }
+
         return -EINVAL;
 
 done:
@@ -1827,6 +1837,8 @@ intel_dp_add_properties(struct intel_dp *intel_dp, struct drm_connector *connect
                 intel_dp->force_audio_property->values[1] = 1;
                 drm_connector_attach_property(connector, intel_dp->force_audio_property, 0);
         }
+
+        intel_attach_broadcast_rgb_property(connector);
 }
 
 void