drm/i915: Handle locking better in i915_sink_crc.

	struct intel_connector *connector;

	struct drm_connector_list_iter conn_iter;

	struct intel_dp *intel_dp = NULL;

	struct drm_modeset_acquire_ctx ctx;

	int ret;

	u8 crc[6];

	drm_modeset_lock_all(dev);

	drm_modeset_acquire_init(&ctx, DRM_MODESET_ACQUIRE_INTERRUPTIBLE);

	drm_connector_list_iter_begin(dev, &conn_iter);

	for_each_intel_connector_iter(connector, &conn_iter) {

		struct drm_crtc *crtc;

		struct drm_connector_state *state;

		if (!connector->base.state->best_encoder)

		if (connector->base.connector_type != DRM_MODE_CONNECTOR_eDP)

			continue;

		crtc = connector->base.state->crtc;

		if (!crtc->state->active)

retry:

		ret = drm_modeset_lock(&dev->mode_config.connection_mutex, &ctx);

		if (ret)

			goto err;

		state = connector->base.state;

		if (!state->best_encoder)

			continue;

		if (connector->base.connector_type != DRM_MODE_CONNECTOR_eDP)

		crtc = state->crtc;

		ret = drm_modeset_lock(&crtc->mutex, &ctx);

		if (ret)

			goto err;

		if (!crtc->state->active)

			continue;

		intel_dp = enc_to_intel_dp(connector->base.state->best_encoder);

		intel_dp = enc_to_intel_dp(state->best_encoder);

		ret = intel_dp_sink_crc(intel_dp, crc);

		if (ret)

			goto out;

			goto err;

		seq_printf(m, "%02x%02x%02x%02x%02x%02x\n",

			   crc[0], crc[1], crc[2],

			   crc[3], crc[4], crc[5]);

		goto out;

err:

		if (ret == -EDEADLK) {

			ret = drm_modeset_backoff(&ctx);

			if (!ret)

				goto retry;

		}

		goto out;

	}

	ret = -ENODEV;

out:

	drm_connector_list_iter_end(&conn_iter);

	drm_modeset_unlock_all(dev);

	drm_modeset_drop_locks(&ctx);

	drm_modeset_acquire_fini(&ctx);

	return ret;

}