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

[Vivek Kasireddy]

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.syrj...@linux.intel.com>
Signed-off-by: Vivek Kasireddy <vivek.kasire...@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