diff -pruN a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
--- a/drivers/gpu/drm/i915/i915_params.c	2018-05-25 07:46:20.000000000 -0700
+++ b/drivers/gpu/drm/i915/i915_params.c	2018-05-26 16:52:37.204352639 -0700
@@ -175,6 +175,10 @@ i915_param_named(enable_dpcd_backlight,
 i915_param_named(enable_gvt, bool, 0400,
 	"Enable support for Intel GVT-g graphics virtualization host support(default:false)");

+i915_param_named_unsafe(glkhdmi, int, 0400,
+       "Enable GLK HDMI workarounds "
+       "(0=none/default, 1=disable HDMI 12bpc, 2=add 50ms delay after transcoder disable to give the level shifter time to settle)");
+
 static __always_inline void _print_param(struct drm_printer *p,
 					 const char *name,
 					 const char *type,
diff -pruN a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
--- a/drivers/gpu/drm/i915/i915_params.h	2018-05-25 07:46:20.000000000 -0700
+++ b/drivers/gpu/drm/i915/i915_params.h	2018-05-26 16:52:37.204352639 -0700
@@ -69,7 +69,8 @@ struct drm_printer;
 	param(bool, nuclear_pageflip, false) \
 	param(bool, enable_dp_mst, true) \
 	param(bool, enable_dpcd_backlight, false) \
-	param(bool, enable_gvt, false)
+	param(bool, enable_gvt, false) \
+	param(int, glkhdmi, CONFIG_I915_GLK_HDMI_NOSIGNAL_WORKAROUND)

 #define MEMBER(T, member, ...) T member;
 struct i915_params {
diff -pruN a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
--- a/drivers/gpu/drm/i915/intel_ddi.c	2018-05-25 07:46:20.000000000 -0700
+++ b/drivers/gpu/drm/i915/intel_ddi.c	2018-05-26 16:52:37.207352625 -0700
@@ -1613,6 +1613,9 @@ void intel_ddi_disable_transcoder_func(s
 	val &= ~(TRANS_DDI_FUNC_ENABLE | TRANS_DDI_PORT_MASK | TRANS_DDI_DP_VC_PAYLOAD_ALLOC);
 	val |= TRANS_DDI_PORT_NONE;
 	I915_WRITE(reg, val);
+
+	if (i915_modparams.glkhdmi == 2)
+		msleep(50);
 }

 bool intel_ddi_connector_get_hw_state(struct intel_connector *intel_connector)
diff -pruN a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
--- a/drivers/gpu/drm/i915/intel_hdmi.c	2018-05-25 07:46:20.000000000 -0700
+++ b/drivers/gpu/drm/i915/intel_hdmi.c	2018-05-26 16:52:37.213352599 -0700
@@ -1350,6 +1350,9 @@ static bool hdmi_12bpc_possible(const st
 	struct drm_connector *connector;
 	int i;

+	if (i915_modparams.glkhdmi == 1)
+		return false;
+
 	if (HAS_GMCH_DISPLAY(dev_priv))
 		return false;

diff -pruN a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
--- a/drivers/gpu/drm/i915/Kconfig	2018-05-25 07:46:20.000000000 -0700
+++ b/drivers/gpu/drm/i915/Kconfig	2018-05-26 16:52:37.197352669 -0700
@@ -126,6 +126,23 @@ config DRM_I915_GVT_KVMGT
 	  Choose this option if you want to enable KVMGT support for
 	  Intel GVT-g.

+choice
+	prompt "Workaround for Gemini-Lake HDMI no signal"
+	depends on DRM_I915
+	config GLK_HDMI_WORKAROUND_0
+		bool "None"
+	config GLK_HDMI_WORKAROUND_1
+		bool "Disable 12bpc HDMI support"
+	config GLK_HDMI_WORKAROUND_2
+		bool "Add 50ms delay after disabling the transcoder"
+endchoice
+
+config I915_GLK_HDMI_NOSIGNAL_WORKAROUND
+	int
+	default 0 if GLK_HDMI_WORKAROUND_0
+	default 1 if GLK_HDMI_WORKAROUND_1
+	default 2 if GLK_HDMI_WORKAROUND_2
+
 menu "drm/i915 Debugging"
 depends on DRM_I915
 depends on EXPERT