[GLK] HDMI Scrambling Issue on Samsung 4K TV
I noticed that HDMI modes that require pixel clock rate > 340 Mhz don't work too well on my Samsung UE43RU7100 TV + Asrock J4105B-ITX board. The issues are:
- Intermittent white dots visible on dark areas of the image
- The TV has a HDMI cable self-test. It always fail when using a HDMI mode that require a pixel clock > 340 Mhz
After some experiments I was able to fix the issues by disabling HDMI Scrambling:
diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
index 2fa9ba3..b258e1d 100644
--- a/drivers/gpu/drm/i915/display/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
@@ -2549,7 +2549,7 @@ int intel_hdmi_compute_config(struct intel_encoder *encoder,
pipe_config->hdmi_scrambling = true;
if (pipe_config->port_clock > 340000) {
- pipe_config->hdmi_scrambling = true;
+ pipe_config->hdmi_scrambling = false;
pipe_config->hdmi_high_tmds_clock_ratio = true;
}
}
After applying this patch all issues are gone. No more white dots, HDMI cable test always passes.
Edited by Sergey