drm/i915: add a "force-dvi" HDMI audio mode

When HDMI-DVI converter is used, it's not only necessary to turn off
audio, but also to disable HDMI_MODE_SELECT and video infoframe. Since
the DVI mode is mainly tied to audio functionality from end user POV,
add a new "force-dvi" audio mode:

	xrandr --output HDMI1 --set audio force-dvi

Note that most users won't need to set this and happily rely on the EDID
based DVI auto detection.
Reported-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.h

@@ -762,6 +762,13 @@ typedef struct drm_i915_private {
 	struct drm_property *force_audio_property;
 } drm_i915_private_t;
 
+enum hdmi_force_audio {
+	HDMI_AUDIO_OFF_DVI = -2,	/* no aux data for HDMI-DVI converter */
+	HDMI_AUDIO_OFF,			/* force turn off HDMI audio */
+	HDMI_AUDIO_AUTO,		/* trust EDID */
+	HDMI_AUDIO_ON,			/* force turn on HDMI audio */
+};
+
 enum i915_cache_level {
 	I915_CACHE_NONE,
 	I915_CACHE_LLC,

drivers/gpu/drm/i915/intel_hdmi.c

@@ -44,7 +44,7 @@ struct intel_hdmi {
 	uint32_t color_range;
 	bool has_hdmi_sink;
 	bool has_audio;
-	int force_audio;
+	enum hdmi_force_audio force_audio;
 	void (*write_infoframe)(struct drm_encoder *encoder,
 				struct dip_infoframe *frame);
 };
@@ -339,7 +339,9 @@ intel_hdmi_detect(struct drm_connector *connector, bool force)
 	if (edid) {
 		if (edid->input & DRM_EDID_INPUT_DIGITAL) {
 			status = connector_status_connected;
-			intel_hdmi->has_hdmi_sink = drm_detect_hdmi_monitor(edid);
+			if (intel_hdmi->force_audio != HDMI_AUDIO_OFF_DVI)
+				intel_hdmi->has_hdmi_sink =
+						drm_detect_hdmi_monitor(edid);
 			intel_hdmi->has_audio = drm_detect_monitor_audio(edid);
 		}
 		connector->display_info.raw_edid = NULL;
@@ -347,8 +349,9 @@ intel_hdmi_detect(struct drm_connector *connector, bool force)
 	}
 
 	if (status == connector_status_connected) {
-		if (intel_hdmi->force_audio)
-			intel_hdmi->has_audio = intel_hdmi->force_audio > 0;
+		if (intel_hdmi->force_audio != HDMI_AUDIO_AUTO)
+			intel_hdmi->has_audio =
+				(intel_hdmi->force_audio == HDMI_AUDIO_ON);
 	}
 
 	return status;
@@ -402,7 +405,7 @@ intel_hdmi_set_property(struct drm_connector *connector,
 		return ret;
 
 	if (property == dev_priv->force_audio_property) {
-		int i = val;
+		enum hdmi_force_audio i = val;
 		bool has_audio;
 
 		if (i == intel_hdmi->force_audio)
@@ -410,13 +413,13 @@ intel_hdmi_set_property(struct drm_connector *connector,
 
 		intel_hdmi->force_audio = i;
 
-		if (i == 0)
+		if (i == HDMI_AUDIO_AUTO)
 			has_audio = intel_hdmi_detect_audio(connector);
 		else
-			has_audio = i > 0;
+			has_audio = (i == HDMI_AUDIO_ON);
 
-		if (has_audio == intel_hdmi->has_audio)
-			return 0;
+		if (i == HDMI_AUDIO_OFF_DVI)
+			intel_hdmi->has_hdmi_sink = 0;
 
 		intel_hdmi->has_audio = has_audio;
 		goto done;

drivers/gpu/drm/i915/intel_modes.c

@@ -84,6 +84,7 @@ int intel_ddc_get_modes(struct drm_connector *connector,
 }
 
 static const char *force_audio_names[] = {
+	"force-dvi",
 	"off",
 	"auto",
 	"on",
@@ -106,7 +107,8 @@ intel_attach_force_audio_property(struct drm_connector *connector)
 			return;
 
 		for (i = 0; i < ARRAY_SIZE(force_audio_names); i++)
-			drm_property_add_enum(prop, i, i-1, force_audio_names[i]);
+			drm_property_add_enum(prop, i, i-2,
+					      force_audio_names[i]);
 
 		dev_priv->force_audio_property = prop;
 	}