[PATCH] drm/i915: Handle sink scrambling for dp dual mode adapters

[Shashank Sharma]

Sink scrambling should be enabled only when the video mode's clock
is > 340Mhz (Until monitor asks us specifically via EDID). When the
source device contains a DP dual mode adapter, it can limit the source
clock to a lesser value then it can, matching adapter's capabilities.

This patch adds a check to consider the adapter's capability, before
touching enabling/dissabling sink scrambling and high TMDS clock ratio.

Signed-off-by: Shashank Sharma <shashank.sharma at intel.com>
---
 drivers/gpu/drm/i915/display/intel_hdmi.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
index 0a6846c5ba95..f62c254c7f8f 100644
--- a/drivers/gpu/drm/i915/display/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
@@ -2909,6 +2909,11 @@ bool intel_hdmi_handle_sink_scrambling(struct intel_encoder *encoder,
 	if (!sink_scrambling->supported)
 		return true;
 
+	/* Scrambling should be enabled/disabled for clocks > 340Mhz only */
+	if (intel_hdmi->dp_dual_mode.type != DRM_DP_DUAL_MODE_NONE &&
+	    intel_hdmi->dp_dual_mode.max_tmds_clock <= 340000)
+		return true;
+
 	DRM_DEBUG_KMS("[CONNECTOR:%d:%s] scrambling=%s, TMDS bit clock ratio=1/%d\n",
 		      connector->base.id, connector->name,
 		      yesno(scrambling), high_tmds_clock_ratio ? 40 : 10);
-- 
2.17.1