drm/i915: lock around link status and link training.

We need to take the connection mutex around the link status
check for non-MST case, but also around the MST link training
on short HPDs.

I suspect we actually should have a dpcd lock in the future as
well, that just lock the local copies of dpcd and flags stored
from that.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index ea6ff71b2910..eb52ecfe14cf 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -3535,11 +3535,13 @@ go_again:
 void
 intel_dp_check_link_status(struct intel_dp *intel_dp)
 {
+        struct drm_device *dev = intel_dp_to_dev(intel_dp);
         struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
         u8 sink_irq_vector;
         u8 link_status[DP_LINK_STATUS_SIZE];
 
-        /* FIXME: This access isn't protected by any locks. */
+        WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
+
         if (!intel_encoder->connectors_active)
                 return;
 
@@ -4058,7 +4060,9 @@ intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port, bool long_hpd)
                          * we'll check the link status via the normal hot plug path later -
                          * but for short hpds we should check it now
                          */
+                        drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
                         intel_dp_check_link_status(intel_dp);
+                        drm_modeset_unlock(&dev->mode_config.connection_mutex);
                 }
         }
         return false;