drm/i915: Skip vcpi allocation for MSTB ports that are gone

Since we need to be able to allow DPMS on->off prop changes after an MST
port has disappeared from the system, we need to be able to make sure we
can compute a config for the resulting atomic commit. Currently this is
impossible when the port has disappeared, since the VCPI slot searching
we try to do in intel_dp_mst_compute_config() will fail with -EINVAL.

Since the only commits we want to allow on no-longer-present MST ports
are ones that shut off display hardware, we already know that no VCPI
allocations are needed. So, hardcode the VCPI slot count to 0 when
intel_dp_mst_compute_config() is called on an MST port that's gone.

Changes since V4:
- Don't use mst_port_gone at all, just check whether or not the drm
  connector is registered - Daniel Vetter

Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20181008232437.5571-5-lyude@redhat.com

1 files changed, 15 insertions, 9 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
index aa21742d8634..0f14c0d1669c 100644
--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -38,11 +38,11 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
         struct intel_dp_mst_encoder *intel_mst = enc_to_mst(&encoder->base);
         struct intel_digital_port *intel_dig_port = intel_mst->primary;
         struct intel_dp *intel_dp = &intel_dig_port->dp;
-        struct intel_connector *connector =
-                to_intel_connector(conn_state->connector);
+        struct drm_connector *connector = conn_state->connector;
+        void *port = to_intel_connector(connector)->port;
         struct drm_atomic_state *state = pipe_config->base.state;
         int bpp;
-        int lane_count, slots;
+        int lane_count, slots = 0;
         const struct drm_display_mode *adjusted_mode = &pipe_config->base.adjusted_mode;
         int mst_pbn;
         bool constant_n = drm_dp_has_quirk(&intel_dp->desc,
@@ -70,17 +70,23 @@ static bool intel_dp_mst_compute_config(struct intel_encoder *encoder,
 
         pipe_config->port_clock = intel_dp_max_link_rate(intel_dp);
 
-        if (drm_dp_mst_port_has_audio(&intel_dp->mst_mgr, connector->port))
+        if (drm_dp_mst_port_has_audio(&intel_dp->mst_mgr, port))
                 pipe_config->has_audio = true;
 
         mst_pbn = drm_dp_calc_pbn_mode(adjusted_mode->crtc_clock, bpp);
         pipe_config->pbn = mst_pbn;
 
-        slots = drm_dp_atomic_find_vcpi_slots(state, &intel_dp->mst_mgr,
-                                              connector->port, mst_pbn);
-        if (slots < 0) {
-                DRM_DEBUG_KMS("failed finding vcpi slots:%d\n", slots);
-                return false;
+        /* Zombie connectors can't have VCPI slots */
+        if (READ_ONCE(connector->registered)) {
+                slots = drm_dp_atomic_find_vcpi_slots(state,
+                                                      &intel_dp->mst_mgr,
+                                                      port,
+                                                      mst_pbn);
+                if (slots < 0) {
+                        DRM_DEBUG_KMS("failed finding vcpi slots:%d\n",
+                                      slots);
+                        return false;
+                }
         }
 
         intel_link_compute_m_n(bpp, lane_count,