[RFC PATCH 7/7] drm/i915: add DisplayPort CEC-Tunneling-over-AUX support

[Hans Verkuil]

From: Hans Verkuil <hans.verkuil at cisco.com>

Implement support for this DisplayPort feature.

The cec device is created whenever it detects an adapter that
has this feature. It is only removed when a new adapter is connected
that does not support this. If a new adapter is connected that has
different properties than the previous one, then the old cec device is
unregistered and a new one is registered to replace the old one.

Signed-off-by: Hans Verkuil <hans.verkuil at cisco.com>
---
 drivers/gpu/drm/i915/Kconfig    | 11 ++++++++++
 drivers/gpu/drm/i915/intel_dp.c | 46 +++++++++++++++++++++++++++++++++++++----
 2 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
index a5cd5dacf055..f317b13a1409 100644
--- a/drivers/gpu/drm/i915/Kconfig
+++ b/drivers/gpu/drm/i915/Kconfig
@@ -124,6 +124,17 @@ config DRM_I915_GVT_KVMGT
 	  Choose this option if you want to enable KVMGT support for
 	  Intel GVT-g.
 
+config DRM_I915_DP_CEC
+	tristate "Enable DisplayPort CEC-Tunneling-over-AUX HDMI support"
+	depends on DRM_I915 && CEC_CORE
+	select DRM_DP_CEC
+	help
+	  Choose this option if you want to enable HDMI CEC support for
+	  DisplayPort/USB-C to HDMI adapters.
+
+	  Note: not all adapters support this feature, and even for those
+	  that do support this often do not hook up the CEC pin.
+
 menu "drm/i915 Debugging"
 depends on DRM_I915
 depends on EXPERT
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index ee77b519835c..38e17ee2548d 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -32,6 +32,7 @@
 #include <linux/notifier.h>
 #include <linux/reboot.h>
 #include <asm/byteorder.h>
+#include <media/cec.h>
 #include <drm/drmP.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_crtc.h>
@@ -1405,6 +1406,7 @@ static void intel_aux_reg_init(struct intel_dp *intel_dp)
 static void
 intel_dp_aux_fini(struct intel_dp *intel_dp)
 {
+	cec_unregister_adapter(intel_dp->aux.cec_adap);
 	kfree(intel_dp->aux.name);
 }
 
@@ -4179,6 +4181,33 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
 	return -EINVAL;
 }
 
+static bool
+intel_dp_check_cec_status(struct intel_dp *intel_dp)
+{
+	bool handled = false;
+
+	for (;;) {
+		u8 cec_irq;
+		int ret;
+
+		ret = drm_dp_dpcd_readb(&intel_dp->aux,
+					DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1,
+					&cec_irq);
+		if (ret < 0 || !(cec_irq & DP_CEC_IRQ))
+			return handled;
+
+		cec_irq &= ~DP_CEC_IRQ;
+		drm_dp_cec_irq(&intel_dp->aux);
+		handled = true;
+
+		ret = drm_dp_dpcd_writeb(&intel_dp->aux,
+					 DP_DEVICE_SERVICE_IRQ_VECTOR_ESI1,
+					 cec_irq);
+		if (ret < 0)
+			return handled;
+	}
+}
+
 static void
 intel_dp_retrain_link(struct intel_dp *intel_dp)
 {
@@ -4553,6 +4582,7 @@ intel_dp_set_edid(struct intel_dp *intel_dp)
 		intel_dp->has_audio = intel_dp->force_audio == HDMI_AUDIO_ON;
 	else
 		intel_dp->has_audio = drm_detect_monitor_audio(edid);
+	cec_s_phys_addr_from_edid(intel_dp->aux.cec_adap, edid);
 }
 
 static void
@@ -4562,6 +4592,7 @@ intel_dp_unset_edid(struct intel_dp *intel_dp)
 
 	kfree(intel_connector->detect_edid);
 	intel_connector->detect_edid = NULL;
+	cec_phys_addr_invalidate(intel_dp->aux.cec_adap);
 
 	intel_dp->has_audio = false;
 }
@@ -4582,13 +4613,17 @@ intel_dp_long_pulse(struct intel_connector *intel_connector)
 	intel_display_power_get(to_i915(dev), intel_dp->aux_power_domain);
 
 	/* Can't disconnect eDP, but you can close the lid... */
-	if (is_edp(intel_dp))
+	if (is_edp(intel_dp)) {
 		status = edp_detect(intel_dp);
-	else if (intel_digital_port_connected(to_i915(dev),
-					      dp_to_dig_port(intel_dp)))
+	} else if (intel_digital_port_connected(to_i915(dev),
+						dp_to_dig_port(intel_dp))) {
 		status = intel_dp_detect_dpcd(intel_dp);
-	else
+		if (status == connector_status_connected)
+			drm_dp_cec_configure_adapter(&intel_dp->aux,
+				     intel_dp->aux.name, dev->dev);
+	} else {
 		status = connector_status_disconnected;
+	}
 
 	if (status == connector_status_disconnected) {
 		memset(&intel_dp->compliance, 0, sizeof(intel_dp->compliance));
@@ -5080,6 +5115,9 @@ intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port, bool long_hpd)
 
 	intel_display_power_get(dev_priv, intel_dp->aux_power_domain);
 
+	if (intel_dp->aux.cec_adap)
+		intel_dp_check_cec_status(intel_dp);
+
 	if (intel_dp->is_mst) {
 		if (intel_dp_check_mst_status(intel_dp) == -EINVAL) {
 			/*
-- 
2.11.0