drm/edid: Allow HDMI infoframe without VIC or S3D

Appedix F of HDMI 2.0 says that some HDMI sink may fail to switch from
3D to 2D mode in a timely fashion if the source simply stops sending the
HDMI infoframe. The suggested workaround is to keep sending the
infoframe even when strictly not necessary (ie. no VIC and no S3D).
HDMI 1.4 does allow for this behaviour, stating that sending the
infoframe is optional in this case.

The infoframe was first specified in HDMI 1.4, so in theory sinks
predating that may not appreciate us sending an uknown infoframe
their way. To avoid regressions let's try to determine if the sink
supports the infoframe or not. Unfortunately there's no direct way
to do that, so instead we'll just check if we managed to parse any
HDMI 1.4 4k or stereo modes from the EDID, and if so we assume the
sink will accept the infoframe. Also if the EDID contains the HDMI
2.0 HDMI Forum VSDB we can assume the sink is prepared to receive
the infoframe.

v2: Fix getting has_hdmi_infoframe from display_info
    Always fail constructing the infoframe if the display
    possibly can't handle it

Cc: Shashank Sharma <shashank.sharma@intel.com>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171113170427.4150-3-ville.syrjala@linux.intel.com

1 files changed, 28 insertions, 6 deletions

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 749d07a01772..9ada0ccf50df 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -3393,6 +3393,7 @@ static int
 do_hdmi_vsdb_modes(struct drm_connector *connector, const u8 *db, u8 len,
 		   const u8 *video_db, u8 video_len)
 {
+	struct drm_display_info *info = &connector->display_info;
 	int modes = 0, offset = 0, i, multi_present = 0, multi_len;
 	u8 vic_len, hdmi_3d_len = 0;
 	u16 mask;
@@ -3520,6 +3521,8 @@ do_hdmi_vsdb_modes(struct drm_connector *connector, const u8 *db, u8 len,
 	}
 
 out:
+	if (modes > 0)
+		info->has_hdmi_infoframe = true;
 	return modes;
 }
 
@@ -4243,6 +4246,8 @@ static void drm_parse_hdmi_forum_vsdb(struct drm_connector *connector,
 	struct drm_display_info *display = &connector->display_info;
 	struct drm_hdmi_info *hdmi = &display->hdmi;
 
+	display->has_hdmi_infoframe = true;
+
 	if (hf_vsdb[6] & 0x80) {
 		hdmi->scdc.supported = true;
 		if (hf_vsdb[6] & 0x40)
@@ -4416,6 +4421,7 @@ static void drm_add_display_info(struct drm_connector *connector,
 	info->cea_rev = 0;
 	info->max_tmds_clock = 0;
 	info->dvi_dual = false;
+	info->has_hdmi_infoframe = false;
 
 	if (edid->revision < 3)
 		return;
@@ -4903,6 +4909,7 @@ s3d_structure_from_display_mode(const struct drm_display_mode *mode)
  * drm_hdmi_vendor_infoframe_from_display_mode() - fill an HDMI infoframe with
  * data from a DRM display mode
  * @frame: HDMI vendor infoframe
+ * @connector: the connector
  * @mode: DRM display mode
  *
  * Note that there's is a need to send HDMI vendor infoframes only when using a
@@ -4913,8 +4920,15 @@ s3d_structure_from_display_mode(const struct drm_display_mode *mode)
  */
 int
 drm_hdmi_vendor_infoframe_from_display_mode(struct hdmi_vendor_infoframe *frame,
+					    struct drm_connector *connector,
 					    const struct drm_display_mode *mode)
 {
+	/*
+	 * FIXME: sil-sii8620 doesn't have a connector around when
+	 * we need one, so we have to be prepared for a NULL connector.
+	 */
+	bool has_hdmi_infoframe = connector ?
+		connector->display_info.has_hdmi_infoframe : false;
 	int err;
 	u32 s3d_flags;
 	u8 vic;
@@ -4922,11 +4936,21 @@ drm_hdmi_vendor_infoframe_from_display_mode(struct hdmi_vendor_infoframe *frame,
 	if (!frame || !mode)
 		return -EINVAL;
 
+	if (!has_hdmi_infoframe)
+		return -EINVAL;
+
 	vic = drm_match_hdmi_mode(mode);
 	s3d_flags = mode->flags & DRM_MODE_FLAG_3D_MASK;
 
-	if (!vic && !s3d_flags)
-		return -EINVAL;
+	/*
+	 * Even if it's not absolutely necessary to send the infoframe
+	 * (ie.vic==0 and s3d_struct==0) we will still send it if we
+	 * know that the sink can handle it. This is based on a
+	 * suggestion in HDMI 2.0 Appendix F. Apparently some sinks
+	 * have trouble realizing that they shuld switch from 3D to 2D
+	 * mode if the source simply stops sending the infoframe when
+	 * it wants to switch from 3D to 2D.
+	 */
 
 	if (vic && s3d_flags)
 		return -EINVAL;
@@ -4935,10 +4959,8 @@ drm_hdmi_vendor_infoframe_from_display_mode(struct hdmi_vendor_infoframe *frame,
 	if (err < 0)
 		return err;
 
-	if (vic)
-		frame->vic = vic;
-	else
-		frame->s3d_struct = s3d_structure_from_display_mode(mode);
+	frame->vic = vic;
+	frame->s3d_struct = s3d_structure_from_display_mode(mode);
 
 	return 0;
 }