From: Heiner Kallweit <hkallweit1@gmail.com>
Date: Fri, 23 Aug 2019 00:52:34 +0200

Typically the Realtek chips are used on Intel platforms and I haven't
seen any such report yet, so it seems to be platform-specific.
Which board (DT config) is it, and can you provide a full dmesg?

Unfortunately on Intel you're not going to be testing the DMA syncing
very much except with full debugging enabled where it'll use bounce
buffers which give a reasonable simulation of what the non-cache-coherent
systems will be dealing with.