(In reply to taijian from comment #9)
> OK, so I did some git-bisect work in order to find where exactly booting
> with amdgpu.dc=0 broke. What I found is attached, although it does not make
> much sense to me...

Indeed, it's pretty much impossible for that change to cause the problem.

Most likely, the issue with amdgpu.dc=0 happens with some probability < 100%,
so you'd have to test longer / several times before declaring a commit as good.
(A commit where the problem occurs can immediately be marked as bad)