[PATCH 3/3] drm/vc4: Attach underscan props to the HDMI connector

[Boris Brezillon]

Now that the plane code takes the underscan setup into account, we can
safely attach the underscan props to the HDMI connector.

We also take care of filling AVI infoframes correctly to expose the
top/botton/left/right bar.

Note that these underscan props match pretty well the
overscan_{left,right,top,bottom} properties defined in config.txt and
parsed by the VC4 firmware.

Signed-off-by: Boris Brezillon <boris.brezillon at bootlin.com>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 1a6db291d48b..17464b5981f9 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -323,6 +323,16 @@ static struct drm_connector *vc4_hdmi_connector_init(struct drm_device *dev,
 			   DRM_MODE_CONNECTOR_HDMIA);
 	drm_connector_helper_add(connector, &vc4_hdmi_connector_helper_funcs);
 
+	/* The hborder and vborder limit is arbitrarily set to 1024 which
+	 * should be more than enough for real use cases. Note that the actual
+	 * limitation comes from the display mode:
+	 *	hborder < hdisplay && vborder < vdisplay
+	 */
+	drm_connector_attach_underscan_properties(connector,
+						  BIT(DRM_UNDERSCAN_OFF) |
+						  BIT(DRM_UNDERSCAN_ON),
+						  1024, 1024);
+
 	connector->polled = (DRM_CONNECTOR_POLL_CONNECT |
 			     DRM_CONNECTOR_POLL_DISCONNECT);
 
@@ -408,6 +418,9 @@ static void vc4_hdmi_write_infoframe(struct drm_encoder *encoder,
 static void vc4_hdmi_set_avi_infoframe(struct drm_encoder *encoder)
 {
 	struct vc4_hdmi_encoder *vc4_encoder = to_vc4_hdmi_encoder(encoder);
+	struct vc4_dev *vc4 = encoder->dev->dev_private;
+	struct vc4_hdmi *hdmi = vc4->hdmi;
+	struct drm_connector_state *cstate = hdmi->connector->state;
 	struct drm_crtc *crtc = encoder->crtc;
 	const struct drm_display_mode *mode = &crtc->state->adjusted_mode;
 	union hdmi_infoframe frame;
@@ -426,6 +439,18 @@ static void vc4_hdmi_set_avi_infoframe(struct drm_encoder *encoder)
 					   vc4_encoder->rgb_range_selectable,
 					   false);
 
+	if (cstate->underscan.mode == DRM_UNDERSCAN_ON) {
+		if (cstate->underscan.hborder) {
+			frame.avi.right_bar = cstate->underscan.hborder / 2;
+			frame.avi.left_bar = frame.avi.right_bar;
+		}
+
+		if (cstate->underscan.vborder) {
+			frame.avi.top_bar = cstate->underscan.vborder / 2;
+			frame.avi.bottom_bar = frame.avi.top_bar;
+		}
+	}
+
 	vc4_hdmi_write_infoframe(encoder, &frame);
 }
 
-- 
2.14.1