AK4375 is a 32-bit stereo DAC with headphones amplifier.
There's no documentation for it on akm.com, and only a brief
datasheet can be found floating on the internets [1].

Thanks to Oriane BAYERD <obayerd@eurocomposant.fr>
for finally answering my inquiries through akm.com, if only to tell
me that this chip is EOL following AKM factory burning in october 2020
and thus no detailed documentation is available anymore...

AK4331 is advertised [2] as pin and register compatible with AK4375
so some scraps of its datasheet were used and this driver might be
used as a base for it, but this is totally untested.

So this driver is mainly based on downstream code [3] and [4]
by Hu Jin from AKM (no known email).

Tested on msm8916-alcatel-idol347 and msm8939-alcatel-idol3,
which both use PLL driven clock with bypass of SRC (sample rate
converter), so only this setup is supported for now.

[1] https://datasheetspdf.com/pdf-file/1400317/AKM/AK4375A/1
[2] https://www.akm.com/content/dam/documents/products/audio/audio-dac/ak4331ecb/ak4331ecb-en-datasheet.pdf
[3] https://github.com/msm8916-mainline/android_kernel_qcom_msm8916/blob/alcatel-idol347/sound/soc/codecs/idol347/ak4375.c
[4] https://github.com/msm8916-mainline/android_kernel_qcom_msm8916/blob/alcatel-idol347/sound/soc/codecs/ak4375.cSigned-off-by: Vincent Knecht <vincent.knecht@mailoo.org>
Link: https://lore.kernel.org/r/20211220193725.2650356-2-vincent.knecht@mailoo.orgSigned-off-by: Mark Brown <broonie@kernel.org>