[bug report] 'ASoC: Intel: haswell: Power transition refactor' and PulseAudio

[Christian Bundy]

After upgrading to Linux 5.8 I discovered an audio issue on my device that was introduced in 8ec7d6043263ecf250b9b7c0dd8ade899487538a [0]. I used 'git bisect' to identify the commit that introduced the bug and have confirmed that reverting the commit resolves the problem

Reproduction:

1. Play any audio via PulseAudio.
2. Observe that the audio output is fuzzy and choppy.

I can use programs like mpv to play audio without PulseAudio, and the audio is fine, but as soon as I open a process that uses PulseAudio it will ruin the audio output for all processes (including mpv) until I reboot.

I'm using a 2015 Chromebook Pixel ("Samus") and have confirmed this problem with a friend who has the same device.

Is there anything I can do to help debug this instead of sending a patch to revert the commit?

Relevant lspci output:

    00:03.0 Audio device: Intel Corporation Broadwell-U Audio Controller (rev 09)
	Subsystem: Intel Corporation Broadwell-U Audio Controller
	Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0, Cache Line Size: 64 bytes
	Interrupt: pin A routed to IRQ 50
	Region 0: Memory at e1218000 (64-bit, non-prefetchable) [size=16K]
	Capabilities: [50] Power Management version 2
		Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
		Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
	Capabilities: [60] MSI: Enable+ Count=1/1 Maskable- 64bit-
		Address: fee00378  Data: 0000
	Capabilities: [70] Express (v1) Root Complex Integrated Endpoint, MSI 00
		DevCap:	MaxPayload 128 bytes, PhantFunc 0
			ExtTag- RBE- FLReset+
		DevCtl:	CorrErr- NonFatalErr- FatalErr- UnsupReq-
			RlxdOrd- ExtTag- PhantFunc- AuxPwr- NoSnoop- FLReset-
			MaxPayload 128 bytes, MaxReadReq 128 bytes
		DevSta:	CorrErr- NonFatalErr- FatalErr- UnsupReq- AuxPwr- TransPend-
	Kernel driver in use: snd_hda_intel
	Kernel modules: snd_hda_intel

[0]: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=8ec7d6043263ecf250b9b7c0dd8ade899487538a