[PATCH v7 06/30] drm/display: hdmi_state_helper: Plumb HDMI 2.0 source scrambling capability

[Cristian Ciocaltea]

Toggle drm_connector_hdmi_state.scrambler_needed flag when the TMDS
character rate exceeds 340 MHz and both the source and the sink advertise
SCDC scrambling capability.  Drivers no longer need to open-code this
check.

According to HDMI 2.0 spec, scrambling is only mandatory above 340 MHz;
the optional sub-340 MHz scrambling path is intentionally not requested.

Once all drivers are converted to advertise the scrambler support, the
unsupported HDMI 2.0 modes could be simply rejected.

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/display/drm_hdmi_state_helper.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
index a96d81cbf94f..7cb880dcedfe 100644
--- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
+++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
@@ -588,6 +588,21 @@ hdmi_compute_clock(const struct drm_connector *connector,
 	if (status != MODE_OK)
 		return -EINVAL;
 
+	if (clock > HDMI_1_3_TMDS_CHAR_RATE_MAX_HZ) {
+		const struct drm_display_info *info = &connector->display_info;
+
+		/*
+		 * TODO: Reject unsupported HDMI 2.0 modes once all drivers
+		 *	 advertise their scrambler capability.
+		 */
+		conn_state->hdmi.scrambler_needed = connector->hdmi.scrambler_supported &&
+						    info->is_hdmi &&
+						    info->hdmi.scdc.supported &&
+						    info->hdmi.scdc.scrambling.supported;
+	} else {
+		conn_state->hdmi.scrambler_needed = false;
+	}
+
 	conn_state->hdmi.tmds_char_rate = clock;
 
 	return 0;

-- 
2.54.0