[RFC] Sound support for Huawei line of AMD laptops using ACP and ES8336 codec

[Marian Postevca]

I have a Huawei Matebook 14 AMD 2021 laptop for which the sound isn't
supported on Linux. On further investigation in Windows and ACPI tables
I could determine that this particular SKU has an ES8336 codec connected
to the CPU ACP module.
The CPU of my laptop is an AMD Ryzen 5 5500U which seems to be codenamed
Lucienne and is a derivation of the Renoir family.
Acording to lspci the ACP is revision 1:

03:00.5 Multimedia controller [0480]: Advanced Micro Devices, Inc. [AMD] Raven/Raven2/FireFlight/Renoir Audio Processor [1022:15e2] (rev 01)
	Subsystem: Device [1e83:3e4d]
	Kernel driver in use: snd_rn_pci_acp3x
	Kernel modules: snd_pci_acp3x, snd_rn_pci_acp3x, snd_pci_acp5x,
	snd_pci_acp6x, snd_acp_pci, snd_rpl_pci_acp6x,
	snd_sof_amd_renoir

I have written a machine driver for this platform and managed to make
the sound and internal microphone work. I am looking to integrate this
support but there are some issues with the current implementation of ACP
support.

As far as I can tell there are 4 directions I could take to add support:

1. A standalone machine driver in sound/soc/amd that uses the platform
  drivers from sound/soc/amd/raven/

2. An embedded driver in sound/soc/amd/acp/acp-legacy-mach.c

3. A standalone machine driver in sound/soc/amd that uses the platform
  drivers from sound/soc/amd/renoir

4. Use the SOF infrastructure

Now as far as I can tell, all of these directions have issues:

1. The pci driver from sound/soc/amd/raven/pci-acp3x.c doesn't support Lucienne
   since it blocks rev 1 devices in :

   /* Raven device detection */
   if (pci->revision != 0x00)
       return -ENODEV;

   This is the approach I took and just changed the check to add support
   for rev 1.
   The sound and internal microphone worked ok and I didn't encounter any
   issues with it. Of course I don't know the internals of ACP and
   don't know what are the differences between rev 0 and rev 1.

2. This approach could work but I would need to change the structure
   acp_card_drvdata and struct snd_soc_dapm_widget acp_widgets,
   to add proper support for jack handling (and maybe some other
   modifications).
   This driver seems to support rev 1 (in sound/soc/amd/acp/acp-pci.c):

   switch (pci->revision) {
	case 0x01:
		chip->name = "acp_asoc_renoir";
		chip->acp_rev = ACP3X_DEV;
		break;

   Also from the module description it seems that these drivers are
   meant only for chromebook support.

3. This seems like it would the best approach in theory, but the problem
   is that the drivers inside only seem to add support for DMIC.

4. I tried to use SOF early when I started tinkering, but I always got a
   timeout during init phase when loading the renoir firmware.

So the reason for this email is to get some idea, on how to best add
support for these laptops.