Rpi 4.4.y adau1977

[andrey2805]

The following 2 commits are result of my work on bring up of ADAU1977 ADC on RPI 2b+.
They add basic support for the codec usage including: Device tree overlay, binding I2S bus and setting I2S mode, clock source and frequency setting according to specification.

[andrey2805]

Forgot to mention that the adau1977-adc is based on HifiBerry DAC driver by Florian Meier and the guides and specs for the HW are at http://www.analog.com/en/products/audio-video/audio-ad-converters/adau1977.html#product-overview

[pelwell]

There are a number of problems with this PR:

1. Overlays belong in arch/arm/boot/dts/overlays.
2. Why aren't the two overlays combined into one?
3. Make the card definition in the overlay (the one with the i2s-controller property) the last fragment - that will allow it to be dynamically unloaded with crashing.
4. Change the comment at the top of the -adc overlay.
5. Overlays need to be compiled, for which you need add them into arch/arm/boot/dts/overlays/Makefile. Please observe alphabetical order.
6. I require an entry in the README for each overlay. Copy the formatting of other entries, insert in alphabetical order and don't use TABs.
7. Your driver needs to be compiled, for which you need to add something to sound/soc/bcm/Makefile.
8. Although copying is allowed, it is polite to mention the author of any work you have copied from.
9. I don't think you need to add an of_device_id/compatible string to the I2C driver. It is a feature of the I2C subsystem that it will look for the element after the comma in a compatible string and look it up using the i2c_device_id table. In fact I think that including an explicit compatible string can stop the device type matching feature from working (the same I2C driver supports multiple devices by returning different IDs for different devices - see the use of ADAU1977 and ADAU1988 in the i2c_device_id table).
10. It is better not to modify upstream code if you can avoid it.

There may be more, but that's enough for now.

[andrey2805]

Thanks for your comments, will rework in short time.

[andrey2805]

Here are the follow-up commits.

[andrey2805]

And another minor typo...

[pelwell]

There is a typo ("conrtrol" -> "control") and whitespace at the end of this line.

[pelwell]

The final pieces you are missing are the additions to bcmrpi_defconfig and bcm2709_defconfig to cause the codec and card driver to be built:

diff --git a/arch/arm/configs/bcm2709_defconfig b/arch/arm/configs/bcm2709_defconfig
index 54c8f4e..47bd1c2 100644
--- a/arch/arm/configs/bcm2709_defconfig
+++ b/arch/arm/configs/bcm2709_defconfig
@@ -861,6 +861,7 @@ CONFIG_SND_BCM2708_SOC_BOOMBERRY_DAC=m
 CONFIG_SND_BCM2708_SOC_BOOMBERRY_DIGI=m
 CONFIG_SND_BCM2708_SOC_IQAUDIO_DAC=m
 CONFIG_SND_BCM2708_SOC_RASPIDAC3=m
+CONFIG_SND_BCM2708_SOC_ADAU1977_ADC=m
 CONFIG_SND_SOC_ADAU1701=m
 CONFIG_SND_SOC_WM8804_I2C=m
 CONFIG_SND_SIMPLE_CARD=m
diff --git a/arch/arm/configs/bcmrpi_defconfig b/arch/arm/configs/bcmrpi_defconfig
index 13471cc..d66fcd4 100644
--- a/arch/arm/configs/bcmrpi_defconfig
+++ b/arch/arm/configs/bcmrpi_defconfig
@@ -853,6 +853,7 @@ CONFIG_SND_BCM2708_SOC_BOOMBERRY_DAC=m
 CONFIG_SND_BCM2708_SOC_BOOMBERRY_DIGI=m
 CONFIG_SND_BCM2708_SOC_IQAUDIO_DAC=m
 CONFIG_SND_BCM2708_SOC_RASPIDAC3=m
+CONFIG_SND_BCM2708_SOC_ADAU1977_ADC=m
 CONFIG_SND_SOC_ADAU1701=m
 CONFIG_SND_SOC_WM8804_I2C=m
 CONFIG_SND_SIMPLE_CARD=m

Make the changes I have suggested, then squash all the commits into one and update your PR using git push -f.

[andrey2805]

Done.

[pelwell]

You still have whitespace at the end of this line.

[pelwell]

Remove the trailing whitespace plus the two dev_info()s, squash and push, and I will merge it.

[andrey2805]

Done.