DisplayLink doesn't work when intel_iommu is enabled

[YuZhang]

I have a DisplayLink product, i.e., a WAVLINK multi-display HDMI adapter, i.e., USB3.0 to HDMI converter.
I run Ubuntu16.04.1 on i3-6100U machine. I need to turn on intel_iommu, however, it seems as if DisplayLink is not compatible with intel_iommu. When intel_iommu is enabled(intel_iommu=on), the extended monitor (DVI-I-1-1) doesn't work. It keeps a black screen while the primary monitor is in a bad status of very low resolution. There is one similar thread on the forum. But the solution is not useful for me since I need to enable intel_iommu but not to disable it.
(http://displaylink.org/forum/showthr...ighlight=iommu)
Could anyone tell me how can I use DisplayLink with intel_iommu enabled?
I have attached the log files collected by DLSupportTool.

Thanks.