[alsa-devel] regression: bad sound card type detection in audio graph

[Kuninori Morimoto]

Hi  Arnaud

Thank you for checking/testing driver

> In our sound card (described here:
> https://github.com/STMicroelectronics/linux/blob/v4.19-stm32mp/arch/arm/boot/dts/stm32mp157c-ev1.dts)
> 
> We declare a normal sound card using the WM8994 codec:
> 
>   Playback: CPU-DAI (SAI2a)-> CODEC-DAI/port0
>   Record: CPU-DAI (SAI2B)<- CODEC-DAI/port1
>   ...
> 
> The WM8994 codec is declared with 2 ports as it supports 2 interfaces.
> 
> When we probe the sound card we are detecting a wrong dai link type
> because the condition
> if (of_get_child_count(codec_port) > 1) return true. The dai link is
> detected as DPCM instead of the expected normal link.

It seems difficult to use WM8994 on my test environment.
And I tried to add 2 ports on my sound codec driver/DT,
but I can't reproduce your issue.
But, I want to solve your issue.

In my understanding, in your case, cpu/codec will be below.

	for Playback
	cpu_ep		= sai2a_endpoint
	codec_ep	= wm8994_tx_endpoint
	codec_port	= wm8994_tx_port

	for Record
	cpu_ep		= sai2b_endpoint
	codec_ep	= wm8994_rx_endpoint
	codec_port	= wm8994_rx_port

> Please could you elaborate a little bit on this criteria for the
> normal/DPCM selection?
> 
> What is you feeling about this limitation. Do you see a way to refine
> the condition to allow normal sound card with multi-port codecs. Or do
> we have to migrate our sound card to DPCM.

If it was DPCM, 1 port is connected from multiple "endpoint".
So, audio-graph-card is checking if it was "multi-endpoint" or not.
"multi-port" is not related to this judgment.

And in your case, if my understanding was correct,
wm8994_tx/rx only have single-endpoint.
so, if (of_get_child_count(codec_port) > 1) return true is a
little bit strange for me.
Can you check what is this codec_port ? I think you can use
printk("%pOF\n", codec_port) for it.