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, 20 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c
index 19c817a2df0c..9698e91f6a37 100644
--- a/drivers/gpu/drm/i915/intel_sdvo.c
+++ b/drivers/gpu/drm/i915/intel_sdvo.c
@@ -93,6 +93,12 @@ struct intel_sdvo {
         uint16_t attached_output;
 
         /**
+         * This is used to select the color range of RBG outputs in HDMI mode.
+         * It is only valid when using TMDS encoding and 8 bit per color mode.
+         */
+        uint32_t color_range;
+
+        /**
          * This is set if we're going to treat the device as TV-out.
          *
          * While we have these nice friendly flags for output types that ought
@@ -1056,6 +1062,8 @@ static void intel_sdvo_mode_set(struct drm_encoder *encoder,
         /* Set the SDVO control regs. */
         if (INTEL_INFO(dev)->gen >= 4) {
                 sdvox = 0;
+                if (intel_sdvo->is_hdmi)
+                        sdvox |= intel_sdvo->color_range;
                 if (INTEL_INFO(dev)->gen < 5)
                         sdvox |= SDVO_BORDER_ENABLE;
                 if (adjusted_mode->flags & DRM_MODE_FLAG_PVSYNC)
@@ -1695,6 +1703,7 @@ intel_sdvo_set_property(struct drm_connector *connector,
 {
         struct intel_sdvo *intel_sdvo = intel_attached_sdvo(connector);
         struct intel_sdvo_connector *intel_sdvo_connector = to_intel_sdvo_connector(connector);
+        struct drm_i915_private *dev_priv = connector->dev->dev_private;
         uint16_t temp_value;
         uint8_t cmd;
         int ret;
@@ -1724,6 +1733,14 @@ intel_sdvo_set_property(struct drm_connector *connector,
                 goto done;
         }
 
+        if (property == dev_priv->broadcast_rgb_property) {
+                if (val == !!intel_sdvo->color_range)
+                        return 0;
+
+                intel_sdvo->color_range = val ? SDVO_COLOR_RANGE_16_235 : 0;
+                goto done;
+        }
+
 #define CHECK_PROPERTY(name, NAME) \
         if (intel_sdvo_connector->name == property) { \
                 if (intel_sdvo_connector->cur_##name == temp_value) return 0; \
@@ -2028,6 +2045,9 @@ intel_sdvo_add_hdmi_properties(struct intel_sdvo_connector *connector)
                 drm_connector_attach_property(&connector->base.base,
                                               connector->force_audio_property, 0);
         }
+
+        if (INTEL_INFO(dev)->gen >= 4 && IS_MOBILE(dev))
+                intel_attach_broadcast_rgb_property(&connector->base.base);
 }
 
 static bool