[PATCH 2/2] drm/i915: sync dp link status checks against atomic commmits

[Daniel Vetter]

Two bits:
- check actual atomic state, the legacy stuff can only be looked at
  from within the atomic_commit_tail function, since it's only
  protected by ordering and not by any locks.

- Make sure we don't wreak the work an ongoing nonblocking commit is
  doing.

v2: We need the crtc lock too, because a plane update might change it
without having to acquire the connection_mutex (Maarten). Use
Maarten's changes for this locking, while keeping the logic that uses
the connection->commit->hw_done signal for syncing with nonblocking
commits.

v3: The initial state objects from the hw state readout do not have a
commit object. Check for that (spotted by CI).

Cc: Manasi Navare <manasi.d.navare at intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
References: https://bugs.freedesktop.org/show_bug.cgi?id=103336
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99272
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 57 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 51 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index cddd96b24878..59189cdee3db 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -4319,6 +4319,8 @@ static void
 intel_dp_check_link_status(struct intel_dp *intel_dp)
 {
 	struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
+	struct drm_connector_state *conn_state =
+		intel_dp->attached_connector->base.state;
 	struct drm_device *dev = intel_dp_to_dev(intel_dp);
 	u8 link_status[DP_LINK_STATUS_SIZE];
 
@@ -4329,10 +4331,16 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
 		return;
 	}
 
-	if (!intel_encoder->base.crtc)
+	if (!conn_state->crtc)
 		return;
 
-	if (!to_intel_crtc(intel_encoder->base.crtc)->active)
+	WARN_ON(!drm_modeset_is_locked(&conn_state->crtc->mutex));
+
+	if (!conn_state->crtc->state->active)
+		return;
+
+	if (conn_state->commit &&
+	    !try_wait_for_completion(&conn_state->commit->hw_done))
 		return;
 
 	/*
@@ -4368,7 +4376,6 @@ intel_dp_check_link_status(struct intel_dp *intel_dp)
 static bool
 intel_dp_short_pulse(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 = 0;
 	u8 old_sink_count = intel_dp->sink_count;
@@ -4408,9 +4415,8 @@ intel_dp_short_pulse(struct intel_dp *intel_dp)
 			DRM_DEBUG_DRIVER("CP or sink specific irq unhandled\n");
 	}
 
-	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
 	intel_dp_check_link_status(intel_dp);
-	drm_modeset_unlock(&dev->mode_config.connection_mutex);
+
 	if (intel_dp->compliance.test_type == DP_TEST_LINK_TRAINING) {
 		DRM_DEBUG_KMS("Link Training Compliance Test requested\n");
 		/* Send a Hotplug Uevent to userspace to start modeset */
@@ -4860,8 +4866,19 @@ intel_dp_detect(struct drm_connector *connector,
 		      connector->base.id, connector->name);
 
 	/* If full detect is not performed yet, do a full detect */
-	if (!intel_dp->detect_done)
+	if (!intel_dp->detect_done) {
+		struct drm_crtc *crtc;
+		int ret;
+
+		crtc = connector->state->crtc;
+		if (crtc) {
+			ret = drm_modeset_lock(&crtc->mutex, ctx);
+			if (ret)
+				return ret;
+		}
+
 		status = intel_dp_long_pulse(intel_dp->attached_connector);
+	}
 
 	intel_dp->detect_done = false;
 
@@ -5146,10 +5163,38 @@ intel_dp_hpd_pulse(struct intel_digital_port *intel_dig_port, bool long_hpd)
 	}
 
 	if (!intel_dp->is_mst) {
+		struct drm_modeset_acquire_ctx ctx;
+		struct drm_connector *connector = &intel_dp->attached_connector->base;
+		struct drm_crtc *crtc;
+		int iret;
+
+		drm_modeset_acquire_init(&ctx, 0);
+retry:
+		iret = drm_modeset_lock(&dev->mode_config.connection_mutex, &ctx);
+		if (iret)
+			goto err;
+
+		crtc = connector->state->crtc;
+		if (crtc) {
+			iret = drm_modeset_lock(&crtc->mutex, &ctx);
+			if (iret)
+				goto err;
+		}
+
 		if (!intel_dp_short_pulse(intel_dp)) {
 			intel_dp->detect_done = false;
 			goto put_power;
 		}
+
+err:
+		if (iret == -EDEADLK) {
+			drm_modeset_backoff(&ctx);
+			goto retry;
+		}
+
+		drm_modeset_drop_locks(&ctx);
+		drm_modeset_acquire_fini(&ctx);
+		WARN(iret, "Acquiring modeset locks failed with %i\n", iret);
 	}
 
 	ret = IRQ_HANDLED;
-- 
2.15.0