[Letux-kernel] omap-abe-twl6040.c vs. ti, audio-routing for Panda and OMAP5

[H. Nikolaus Schaller]

Hi Tony,

> Am 17.02.2023 um 07:57 schrieb Tony Lindgren <tony at atomide.com>:
> 
> * H. Nikolaus Schaller <hns at goldelico.com> [230216 11:01]:
>> a) remove all entries from DTS since they are a subset of the driver code
> 
> If they are driver internal data and not ASoC generic bindings or audio
> graph stuff,

Well, I don't know exactly what they are good for...

> you might be able to get away with setting the routing in
> the driver based on the device specifc compatible value.

I guess they are intended for defining board specific routes like Handsfree speakers available
or a microphone connector or alike.

But the table in the driver is just a superset of what panda-common or omap5-common defines in the DTS.
So nothing would be missing (except a capability to reduce the list of routes) if we take only this.

> 
> Sorry I don't really know anything about this.. But in general avoiding
> custom dts bindings is the way to go.

Good point since this ti,audio-routing is a vendor-specific extension.

It is used by
davinci-evm-audio.txt
omap-abe-twl6040.txt
omap-twl4030.txt

> And using the standard audio graph
> bindings where possible between devices might solve some issues, not sure
> if it applies to this case though.

On the other hand it seems to be a common vendor/driver specific scheme for others
as well. I find bindings for:

allwinner,audio-routing
atmel,audio-routing
nvidia,audio-routing
qcom,audio-routing
samsung,audio-routing

some even converted to .yaml.

An example being:
arch/arm/boot/dts/exynos5422-odroid.dts + sound/soc/samsung/odroid.c

There, the driver code also has an internal table (odroid_dapm_routes) but some logic which
seems to be related to "old DTS":
https://elixir.bootlin.com/linux/v6.2-rc8/source/sound/soc/samsung/odroid.c#L249

So it seems to be a common pattern to define the routes not in the driver but in the DTS now
and have the internal table only as a fallback?

This would mean to ignore the internal table if there is something in the DTS.

Maybe Peter has a good idea how to proceed.

BR and thanks,
Nikolaus