From: Dave Airlie <airl...@redhat.com>

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.

Signed-off-by: Dave Airlie <airl...@redhat.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 0f05b88..145ac7c 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -3437,6 +3437,7 @@ intel_dp_handle_test_request(struct intel_dp *intel_dp)
 static int
 intel_dp_check_mst_status(struct intel_dp *intel_dp)
 {
+       struct drm_device *dev = intel_dp_to_dev(intel_dp);
        bool bret;
 
        if (intel_dp->is_mst) {
@@ -3449,12 +3450,14 @@ go_again:
                if (bret == true) {
 
                        /* check link status - esi[10] = 0x200c */
+                       drm_modeset_lock(&dev->mode_config.connection_mutex, 
NULL);
                        if (intel_dp->active_mst_links && 
!drm_dp_channel_eq_ok(&esi[10], intel_dp->lane_count)) {
                                DRM_DEBUG_KMS("channel EQ not ok, 
retraining\n");
                                intel_dp_start_link_train(intel_dp);
                                intel_dp_complete_link_train(intel_dp);
                                intel_dp_stop_link_train(intel_dp);
                        }
+                       drm_modeset_unlock(&dev->mode_config.connection_mutex);
 
                        DRM_DEBUG_KMS("got esi %02x %02x %02x\n", esi[0], 
esi[1], esi[2]);
                        ret = drm_dp_mst_hpd_irq(&intel_dp->mst_mgr, esi, 
&handled);
@@ -3502,10 +3505,13 @@ 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];
 
+       WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
+
        /* FIXME: This access isn't protected by any locks. */
        if (!intel_encoder->connectors_active)
                return;
@@ -4021,7 +4027,9 @@ 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;
-- 
1.9.3

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