Sorry, I forgot the "fixes:" in commit
6726ca1a2d531f5a6efc1f785b15606ce837c4dc
I was hoping DRM maintainers would pick it up before it hit mainline, but it hasn't happened.
Please apply to 5.6.x
The driver is new in 5.6 and this fix is merged for 5.7 already.
Sorry for the inconvenience,
Torsten