[alsa-devel] Porting WM8904 codec to new board - trying to get ALSA aplay going

[Nounou Dadoun]

Not sure whether this should go to the dev or users list (or somewhere in between) so I'll start off trying both.

I'm trying to port a wm8904 audio driver/codec to a new board and the new board uses a device tree configuration which is new to both me and our project. The target arm board uses a linux 3-10 kernel, I have the wm8904 on the i2c bus and configured the Sound in the device tree to use an i2s controller. The codec and platform driver are modprobed on startup.  

I've made a lot of progress, I (finally!) have the codec loading/modprobed properly and the platform driver probed and successful (up to a point), so I have in the serial log:
[    6.766524] snd_soc_card_avigilon sound.3:  wm8904-hifi <-> 6000a000.i2s mapping ok

And at the console:
# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: AVIGILONWM8904 [AVIGILON-WM8904], device 0: WM8904-STREAM wm8904-hifi-0 []
  Subdevices: 1/1
  Subdevice #0: subdevice #0
# ls /proc/asound/
AVIGILONWM8904  card0           cards           devices         pcm             timers          version
# cat /proc/asound/cards
 0 [AVIGILONWM8904 ]: AVIGILON-WM8904 - AVIGILON-WM8904
                      AVIGILON-WM8904

But when I try to play a wave file, I get (no sound and):
# aplay -v audiocheck.net_sin_220Hz_0dBFS_10s.wav
Playing WAVE 'audiocheck.net_sin_220Hz_0dBFS_10s.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, Mono
aplay: set_params:1297: Unable to install hw params:
ACCESS:  RW_INTERLEAVED
FORMAT:  S16_LE
SUBFORMAT:  STD
SAMPLE_BITS: 16
FRAME_BITS: 16
CHANNELS: 1
RATE: 44100
PERIOD_TIME: (46439 46440)
PERIOD_SIZE: 2048
PERIOD_BYTES: 4096
PERIODS: 11
BUFFER_TIME: (510839 510840)
BUFFER_SIZE: 22528
BUFFER_BYTES: 45056
TICK_TIME: 0
#
 
But (encouragingly) when I try this, I get my trace statement from the platform driver:
[ 3794.140675] Calling avigilon_board_startup
in the serial log.

>From the canonical/generic platform driver file, the soc_snd_probe  probe routine seems to be doing a bunch of dai link configuration and other stuff (including reading values out of the device tree) which I'm not currently doing in my equivalent probe routine. (And which I haven't been able to find any documentation for.)
 
So a few questions:

Am I correct in assuming that the " Unable to install hw params " error indicates that something is missing at the board probe level?  Any suggestions about what's necessary to get it going?

Is there any documentation about what the board probe should be doing to set up the hardware for playback properly?

Is the board startup routine required to do anything?  (It didn't in the non-device tree implementation which I'm taking it from.)

Any other useful hints or pointers?  Is there a question which I should be asking which I'm not?

Thanks in advance for any assistance which you might be able to provide, my progress to date has involved a lot of trial and error and has been much slower than I would like! ... N

Nou Dadoun
Senior Firmware Developer, Security Specialist


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