[PATCH 2/5] drm/i915: Reinitialize sink scrambling/TMDS clock ratio on HPD

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

The LG 4k TV I have doesn't deassert HPD when I turn the TV off, but
when I turn it back on it will pulse the HPD line. By that time it has
forgotten everything we told it about scrambling and the clock ratio.
Hence if we want to get a picture out if it again we have to tell it
whether we're currently sending scrambled data or not. Implement
that via the encoder->hotplug() hook.

v2: Force a full modeset to not follow the HDMI 2.0 spec more
    closely (Shashank)

Cc: Shashank Sharma <shashank.sharma at intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_ddi.c | 146 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 145 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 1aeae3e97013..25793bdc692f 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -25,6 +25,7 @@
  *
  */
 
+#include <drm/drm_scdc_helper.h>
 #include "i915_drv.h"
 #include "intel_drv.h"
 
@@ -2756,6 +2757,146 @@ intel_ddi_init_dp_connector(struct intel_digital_port *intel_dig_port)
 	return connector;
 }
 
+static int modeset_pipe(struct drm_crtc *crtc,
+			struct drm_modeset_acquire_ctx *ctx)
+{
+	struct drm_atomic_state *state;
+	struct drm_crtc_state *crtc_state;
+	int ret;
+
+	state = drm_atomic_state_alloc(crtc->dev);
+	if (!state)
+		return -ENOMEM;
+
+	state->acquire_ctx = ctx;
+
+	crtc_state = drm_atomic_get_crtc_state(state, crtc);
+	if (IS_ERR(crtc_state)) {
+		ret = PTR_ERR(crtc_state);
+		goto out;
+	}
+
+	crtc_state->mode_changed = true;
+
+	ret = drm_atomic_add_affected_connectors(state, crtc);
+	if (ret)
+		goto out;
+
+	ret = drm_atomic_add_affected_planes(state, crtc);
+	if (ret)
+		goto out;
+
+	ret = drm_atomic_commit(state);
+	if (ret)
+		goto out;
+
+	return 0;
+
+ out:
+	drm_atomic_state_put(state);
+
+	return ret;
+}
+
+static int intel_hdmi_reset_link(struct intel_encoder *encoder,
+				 struct drm_modeset_acquire_ctx *ctx)
+{
+	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
+	struct intel_hdmi *hdmi = enc_to_intel_hdmi(&encoder->base);
+	struct intel_connector *connector = hdmi->attached_connector;
+	struct i2c_adapter *adapter =
+		intel_gmbus_get_adapter(dev_priv, hdmi->ddc_bus);
+	struct drm_connector_state *conn_state;
+	struct intel_crtc_state *crtc_state;
+	struct intel_crtc *crtc;
+	u8 config;
+	int ret;
+
+	if (!connector || connector->base.status != connector_status_connected)
+		return 0;
+
+	ret = drm_modeset_lock(&dev_priv->drm.mode_config.connection_mutex, ctx);
+	if (ret)
+		return ret;
+
+	conn_state = connector->base.state;
+
+	crtc = to_intel_crtc(conn_state->crtc);
+	if (!crtc)
+		return 0;
+
+	ret = drm_modeset_lock(&crtc->base.mutex, ctx);
+	if (ret)
+		return ret;
+
+	crtc_state = to_intel_crtc_state(crtc->base.state);
+
+	WARN_ON(!intel_crtc_has_type(crtc_state, INTEL_OUTPUT_HDMI));
+
+	if (!crtc_state->base.active)
+		return 0;
+
+	if (!crtc_state->hdmi_high_tmds_clock_ratio &&
+	    !crtc_state->hdmi_scrambling)
+		return 0;
+
+	if (conn_state->commit &&
+	    !try_wait_for_completion(&conn_state->commit->hw_done))
+		return 0;
+
+	ret = drm_scdc_readb(adapter, SCDC_TMDS_CONFIG, &config);
+	if (ret < 0) {
+		DRM_ERROR("Failed to read TMDS config: %d\n", ret);
+		return 0;
+	}
+
+	if (!!(config & SCDC_TMDS_BIT_CLOCK_RATIO_BY_40) ==
+	    crtc_state->hdmi_high_tmds_clock_ratio &&
+	    !!(config & SCDC_SCRAMBLING_ENABLE) ==
+	    crtc_state->hdmi_scrambling)
+		return 0;
+
+	/*
+	 * HDMI 2.0 says that one should not send scrambled data
+	 * prior to configuring the sink scrambling, and that
+	 * TMDS clock/data transmission should be suspended when
+	 * changing the TMDS clock rate in the sink. So let's
+	 * just do a full modeset here, even though some sinks
+	 * would be perfectly happy if were to just reconfigure
+	 * the SCDC settings on the fly.
+	 */
+	return modeset_pipe(&crtc->base, ctx);
+}
+
+static bool intel_ddi_hotplug(struct intel_encoder *encoder,
+			      struct intel_connector *connector)
+{
+	struct drm_modeset_acquire_ctx ctx;
+	bool changed;
+	int ret;
+
+	changed = intel_encoder_hotplug(encoder, connector);
+
+	drm_modeset_acquire_init(&ctx, 0);
+
+	for (;;) {
+		ret = intel_hdmi_reset_link(encoder, &ctx);
+
+		if (ret == -EDEADLK) {
+			drm_modeset_backoff(&ctx);
+			continue;
+		}
+
+		break;
+	}
+
+	drm_modeset_drop_locks(&ctx);
+	drm_modeset_acquire_fini(&ctx);
+	WARN(ret, "Acquiring modeset locks failed with %i\n", ret);
+
+	return changed;
+}
+
 static struct intel_connector *
 intel_ddi_init_hdmi_connector(struct intel_digital_port *intel_dig_port)
 {
@@ -2866,7 +3007,10 @@ void intel_ddi_init(struct drm_i915_private *dev_priv, enum port port)
 	drm_encoder_init(&dev_priv->drm, encoder, &intel_ddi_funcs,
 			 DRM_MODE_ENCODER_TMDS, "DDI %c", port_name(port));
 
-	intel_encoder->hotplug = intel_encoder_hotplug;
+	if (init_hdmi)
+		intel_encoder->hotplug = intel_ddi_hotplug;
+	else
+		intel_encoder->hotplug = intel_encoder_hotplug;
 	intel_encoder->compute_output_type = intel_ddi_compute_output_type;
 	intel_encoder->compute_config = intel_ddi_compute_config;
 	intel_encoder->enable = intel_enable_ddi;
-- 
2.13.6