ASoC: Add AK4375 support

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.c

Signed-off-by: Vincent Knecht <vincent.knecht@mailoo.org>
Link: https://lore.kernel.org/r/20211220193725.2650356-2-vincent.knecht@mailoo.org
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/Kconfig

@@ -41,6 +41,7 @@ config SND_SOC_ALL_CODECS
 	imply SND_SOC_ADS117X
 	imply SND_SOC_AK4104
 	imply SND_SOC_AK4118
+	imply SND_SOC_AK4375
 	imply SND_SOC_AK4458
 	imply SND_SOC_AK4535
 	imply SND_SOC_AK4554
@@ -523,6 +524,16 @@ config SND_SOC_AK4118
 	depends on I2C
 	select REGMAP_I2C
 
+config SND_SOC_AK4375
+	tristate "AKM AK4375 CODEC"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  Enable support for the Asahi-Kasei AK4375 codec.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called snd-soc-ak4375.
+
 config SND_SOC_AK4458
 	tristate "AKM AK4458 CODEC"
 	depends on I2C

sound/soc/codecs/Makefile

@@ -34,6 +34,7 @@ snd-soc-adav803-objs := adav803.o
 snd-soc-ads117x-objs := ads117x.o
 snd-soc-ak4104-objs := ak4104.o
 snd-soc-ak4118-objs := ak4118.o
+snd-soc-ak4375-objs := ak4375.o
 snd-soc-ak4458-objs := ak4458.o
 snd-soc-ak4535-objs := ak4535.o
 snd-soc-ak4554-objs := ak4554.o
@@ -371,6 +372,7 @@ obj-$(CONFIG_SND_SOC_ADAV803)  += snd-soc-adav803.o
 obj-$(CONFIG_SND_SOC_ADS117X)	+= snd-soc-ads117x.o
 obj-$(CONFIG_SND_SOC_AK4104)	+= snd-soc-ak4104.o
 obj-$(CONFIG_SND_SOC_AK4118)	+= snd-soc-ak4118.o
+obj-$(CONFIG_SND_SOC_AK4375)	+= snd-soc-ak4375.o
 obj-$(CONFIG_SND_SOC_AK4458)	+= snd-soc-ak4458.o
 obj-$(CONFIG_SND_SOC_AK4535)	+= snd-soc-ak4535.o
 obj-$(CONFIG_SND_SOC_AK4554)	+= snd-soc-ak4554.o