Re: [PATCH 4/7] ASoC: soc-dai: define TDM idle behaviour modes

[Mark Brown <broonie@kernel.org>]

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On Wed, Dec 10, 2025 at 01:57:50PM +1000, James Calligeros wrote:

> We have the use case where a codec enjoys exclusive use of a bus. For
> these, the codec can transmit 0 on any unused slots to hold the bus.

> We also have the case where multiple codecs share a single bus. One
> codec can weakly pull the bus low when it's not being actively driven by
> any of the attached codecs.

Or configure so you don't have any idle slots.

> However, a number of machines split six codecs into groups of three
> across two electrical lines and then OR them at the receiving
> port such that they appear on a single bus at the SoC. Because the two
> data lines are ORed at the receiver, we have to guarantee that line B is
> zero while line A is active, and vice versa. To do this, we set a single codec
> from each group to zero-fill during the active slots of the other group.

So this is an actual logical OR gate somewhere rather than a direct
electrical connection?

It'd be good to have an explanation more like this in the commit
messages to make it clearer to users what this is intended to do.

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