[Intel-gfx] [PATCH] drm/i915/hdmi: Go for scrambling only if platform supports TMDS clock > 340MHz

[Ankit Nautiyal]

There are cases, where devices have an HDMI1.4 retimer, and TMDS clock rate
is capped to 340MHz via VBT. In such cases scrambling might be supported
by the platform and an HDMI2.0 sink for lower TMDS rates, but not
supported by the retimer, causing blankouts.

So avoid enabling scrambling, if the TMDS clock is capped to <= 340MHz.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
---
 drivers/gpu/drm/i915/display/intel_hdmi.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
index efa2da080f62..c124fe667bc0 100644
--- a/drivers/gpu/drm/i915/display/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
@@ -2244,6 +2244,11 @@ static bool intel_hdmi_is_cloned(const struct intel_crtc_state *crtc_state)
 		!is_power_of_2(crtc_state->uapi.encoder_mask);
 }
 
+static bool source_can_support_scrambling(struct intel_encoder *encoder)
+{
+	return intel_hdmi_source_max_tmds_clock(encoder) > 340000;
+}
+
 int intel_hdmi_compute_config(struct intel_encoder *encoder,
 			      struct intel_crtc_state *pipe_config,
 			      struct drm_connector_state *conn_state)
@@ -2301,7 +2306,7 @@ int intel_hdmi_compute_config(struct intel_encoder *encoder,
 
 	pipe_config->lane_count = 4;
 
-	if (scdc->scrambling.supported && DISPLAY_VER(dev_priv) >= 10) {
+	if (scdc->scrambling.supported && source_can_support_scrambling(encoder)) {
 		if (scdc->scrambling.low_rates)
 			pipe_config->hdmi_scrambling = true;
 
-- 
2.25.1