[Intel-gfx] [PATCH v1 2/2] drm/i915: Reject the atomic modeset if an associated Type-C port is disconnected

[Vivek Kasireddy <vivek.kasireddy@intel.com>]

Although, doing a modeset on any disconnected connector might be futile,
it can be particularly problematic if the connector is a Type-C port
without a sink. And, the spec only says "Display software must not use
a disconnected port" while referring to the Type-C DDI seqeuence, it does
not spell out what happens if such an attempt is made. Experimental results
have shown that this can lead to serious issues including a system hang.
Therefore, reject the atomic modeset if we detect that the Type-C port
is not connected.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
---
 drivers/gpu/drm/i915/display/intel_atomic.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_atomic.c b/drivers/gpu/drm/i915/display/intel_atomic.c
index 40da7910f845..40576964b8c1 100644
--- a/drivers/gpu/drm/i915/display/intel_atomic.c
+++ b/drivers/gpu/drm/i915/display/intel_atomic.c
@@ -114,6 +114,8 @@ int intel_digital_connector_atomic_set_property(struct drm_connector *connector,
 int intel_digital_connector_atomic_check(struct drm_connector *conn,
 					 struct drm_atomic_state *state)
 {
+	struct drm_device *dev = conn->dev;
+	struct drm_i915_private *dev_priv = to_i915(dev);
 	struct drm_connector_state *new_state =
 		drm_atomic_get_new_connector_state(state, conn);
 	struct intel_digital_connector_state *new_conn_state =
@@ -122,6 +124,10 @@ int intel_digital_connector_atomic_check(struct drm_connector *conn,
 		drm_atomic_get_old_connector_state(state, conn);
 	struct intel_digital_connector_state *old_conn_state =
 		to_intel_digital_connector_state(old_state);
+	struct intel_encoder *encoder =
+		intel_attached_encoder(to_intel_connector(conn));
+	struct intel_digital_port *dig_port =
+		encoder ? enc_to_dig_port(encoder) : NULL;
 	struct drm_crtc_state *crtc_state;
 
 	intel_hdcp_atomic_check(conn, old_state, new_state);
@@ -131,6 +137,20 @@ int intel_digital_connector_atomic_check(struct drm_connector *conn,
 
 	crtc_state = drm_atomic_get_new_crtc_state(state, new_state->crtc);
 
+	/*
+	 * The spec says that it is not safe to use a disconnected Type-C port.
+	 * Therefore, check to see if this connector is connected and reject
+	 * the modeset if there is no sink detected.
+	 */
+	if (dig_port && !dig_port->connected(encoder) &&
+	    intel_phy_is_tc(dev_priv,
+	    intel_port_to_phy(dev_priv, encoder->port))) {
+		drm_dbg_atomic(&dev_priv->drm,
+			       "[CONNECTOR:%d:%s] is not connected; rejecting the modeset\n",
+			       conn->base.id, conn->name);
+		return -EINVAL;
+	}
+
 	/*
 	 * These properties are handled by fastset, and might not end
 	 * up in a modeset.
-- 
2.35.1