[PATCH 5/6] drm/i915: enable scrambling

[Shashank Sharma]

Geminilake platform has a native HDMI 2.0 controller, and is
capable of driving pixel-clocks upto 594Mhz. HDMI 2.0 spec
mendates scrambling for these higher clocks, for reduced RF footprint.

This patch checks if the monitor supports scrambling, and if required,
enables it during the modeset.

Signed-off-by: Shashank Sharma <shashank.sharma at intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h   |  2 ++
 drivers/gpu/drm/i915/intel_ddi.c  |  5 +++++
 drivers/gpu/drm/i915/intel_drv.h  |  2 ++
 drivers/gpu/drm/i915/intel_hdmi.c | 42 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 51 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 495b789..cc85892 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -7807,6 +7807,8 @@ enum {
 #define  TRANS_DDI_EDP_INPUT_C_ONOFF	(6<<12)
 #define  TRANS_DDI_DP_VC_PAYLOAD_ALLOC	(1<<8)
 #define  TRANS_DDI_BFI_ENABLE		(1<<4)
+#define  TRANS_DDI_HIGH_TMDS_CHAR_RATE	(1<<4)
+#define  TRANS_DDI_HDMI_SCRAMBLING	(1<<0)
 
 /* DisplayPort Transport Control */
 #define _DP_TP_CTL_A			0x64040
diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 9a9a670..aea81ce 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -1278,6 +1278,11 @@ void intel_ddi_enable_transcoder_func(struct drm_crtc *crtc)
 			temp |= TRANS_DDI_MODE_SELECT_HDMI;
 		else
 			temp |= TRANS_DDI_MODE_SELECT_DVI;
+
+		if (IS_GEMINILAKE(dev_priv)) {
+			temp |= intel_hdmi_check_scrambling(intel_encoder,
+				&intel_crtc->config->base.adjusted_mode);
+		}
 	} else if (type == INTEL_OUTPUT_ANALOG) {
 		temp |= TRANS_DDI_MODE_SELECT_FDI;
 		temp |= (intel_crtc->config->fdi_lanes - 1) << 1;
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 393f243..aafce7f 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1588,6 +1588,8 @@ void intel_hdmi_init_connector(struct intel_digital_port *intel_dig_port,
 bool intel_hdmi_compute_config(struct intel_encoder *encoder,
 			       struct intel_crtc_state *pipe_config,
 			       struct drm_connector_state *conn_state);
+uint32_t intel_hdmi_check_scrambling(struct intel_encoder *intel_encoder,
+				struct drm_display_mode *mode);
 void intel_dp_dual_mode_set_tmds_output(struct intel_hdmi *hdmi, bool enable);
 
 
diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
index ebae2bd..92dd9bc 100644
--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -1795,6 +1795,48 @@ static void intel_hdmi_destroy(struct drm_connector *connector)
 	intel_hdmi->aspect_ratio = HDMI_PICTURE_ASPECT_NONE;
 }
 
+static void
+intel_hdmi_enable_scrambling(struct drm_connector *connector)
+{
+	struct drm_i915_private *dev_priv = connector->dev->dev_private;
+	struct intel_hdmi *intel_hdmi = intel_attached_hdmi(connector);
+	struct i2c_adapter *adapter =
+			intel_gmbus_get_adapter(dev_priv, intel_hdmi->ddc_bus);
+
+	if (!drm_enable_scrambling(connector, adapter, true))
+		DRM_ERROR("Request to enable scrambling failed\n");
+}
+
+uint32_t intel_hdmi_check_scrambling(struct intel_encoder *intel_encoder,
+				struct drm_display_mode *mode)
+{
+	struct intel_hdmi *intel_hdmi = enc_to_intel_hdmi(&intel_encoder->base);
+	struct drm_connector *connector = &intel_hdmi->attached_connector->base;
+	struct drm_hdmi_info *hdmi_info = &connector->display_info.hdmi_info;
+	uint32_t hdmi_config = 0;
+
+	DRM_DEBUG_KMS("Checking scrambling for enc:%s connector:%s\n",
+			intel_encoder->base.name, connector->name);
+
+	if (mode->clock < 340000) {
+		if (hdmi_info->scr_info.low_clocks) {
+			intel_hdmi_enable_scrambling(connector);
+			hdmi_config |= TRANS_DDI_HDMI_SCRAMBLING;
+		}
+		return hdmi_config;
+	}
+
+	/* Enable scrambling for clocks > 340M */
+	if (hdmi_info->scr_info.supported) {
+		intel_hdmi_enable_scrambling(connector);
+		hdmi_config |= TRANS_DDI_HDMI_SCRAMBLING;
+	}
+
+	/* Scrambling or not, if clock > 340M, set high char rate */
+	hdmi_config |= TRANS_DDI_HIGH_TMDS_CHAR_RATE;
+	return hdmi_config;
+}
+
 static u8 intel_hdmi_ddc_pin(struct drm_i915_private *dev_priv,
 			     enum port port)
 {
-- 
1.9.1