[alsa-devel] ASoC: Intel: Enabling LPE audio over I2S on Intel Atom E3815

[Shrirang Bagul]

Hi,

I'm attempting to enable audio on Intel Atom E3815. I have a board with RT5660
codec from Realtek connected to the SoC over I2S2. The codec can be configured
over I2C bus. The board supports External Mic In and Line Out connections for
audio.

I am running Ubuntu 16.04 LTS with kernel v4.4.

To support RT5660 codec, I have backported patches -
d01580c ASoC: rt5660: enable MCLK detection
2b26dd4 ASoC: rt5660: add rt5660 codec driver
from https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git
topic/rt5660 branch

To support I2S_CLK using MCLK I've also backported the patch to support PMC
platform clocks -
[13/17] clk: x86: Add Atom PMC platform clocks (https://patchwork.kernel.org/pat
ch/9277989/)

To understand the I2S over LPE architecture for audio I'm referring to the Intel
Atom Processor E3800: Datasheet (http://www.intel.com/content/dam/www/public/us/
en/documents/datasheets/atom-e3800-family-datasheet.pdf) and discussions on
alsa-devel mailing list thread: http://mailman.alsa-project.org/pipermail/alsa-d
evel/2015-November/100303.html

After implementing the machine driver byt-rt5660.c (by referring to byt-
rt5640.c), the CPU DAI baytrail-pcm-audio is registered successfully and the
fw_sst_0f28.bin-48kHz_i2s_master firmware also is loaded without any errors. It
is possible to configure the codec controls using alsamixer. 

However, an attempt to record results in an empty PCM file and no audio is heard
 if I try to playback using aplay.

I'm clueless on how to proceed from this point onward in getting the audio to
work on this board. The ouput of alsa-info.sh, clk_summary & gpio config from
debugfs and dmesg log is attached with this message. I have published the source
code here: http://kernel.ubuntu.com/git/snb/ubuntu-xenial.git/log/?h=x-master-au
dio-test

I would highly appreciate your help!

-Shrirang
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