snd_hda_intel/sst-acpi sound breakage on suspend/resume since 5.6-rc1

[Pierre-Louis Bossart]

>>> While 5.5.x works fine, mainline as of ac309e7744be (v5.6-rc6+) causes me
>>> some sound-related trouble: after boot, the sound works fine -- but once I
>>> suspend and resume my broadwell-based XPS13, I need to switch to headphone
>>> and back to speaker to hear something. But what I hear isn't music but
>>> garbled output.

It's my understanding that the use of the haswell driver is opt-in for 
Dell XPS13 9343. When we run the SOF driver on this device, we have to 
explicitly bypass an ACPI quirk that forces HDAudio to be used:

https://github.com/thesofproject/linux/commit/944b6a2d620a556424ed4195c8428485fcb6c2bd

Have you tried to run in plain vanilla HDAudio mode?