[Bug 106250] Regression with Dell TB16 dock and Linux kernel 4.16.x

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=106250

--- Comment #6 from Stanislav Lisovskiy <stanislav.lisovskiy at intel.com> ---
I think, I could fix the mentioned above issues, at least on mine machine.
The issue here actually consists of two issues: first one is something about
Thunderbolt docking station initialization, it seems that it doesn't work
properly if it is used as a separate module(periodically I had disconnecting
mouse and keyboard, also dislpay). After I started using Thunderbolt as part of
kernel it got significantly better.
The second one, i.e black screen seems to be caused by wrong watermark
calculations, after adding drm.debug I could see multiple error messages from
skl_compute_wm function telling that "requested configuration exceeds maximum
wm level". To check this hypothesis, I've implemented a small hack, so that if
required res_blocks turns out to be >= than ddb_allocation that just assign.
After those changes I don't get black screen anymore, even after multiple
connecting/disconnecting Thunderbolts USB-C cable. 

However some USB peripherals might still stop working after that, which I
believe is a USB hub related problem.

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