Re: [PATCH 13/13] ASoC: ti: davinci-i2s: Opitonally drive DX pin during capture streams

[Péter Ujfalusi <peter.ujfalusi@xxxxxxxxx>]

On 20/03/2024 17:42, Péter Ujfalusi wrote:
>>> On 15/03/2024 13:27, Bastien Curutchet wrote:
>>>> The McBSP's DX pin that outputs serial data during playback streams can
>>>> be used during capture streams to repeatedly output a chosen pattern.
>>>> For instance, this can be useful to drive an active-low signal during
>>>> captures (by choosing <0> as output pattern).
>>>
>>> Are there really any other use of this than to pull down or up the DX
>>> pin (0 or 0xffff)
>>
>> I don't know, indeed today I can only think about these two patterns.
>> I tried to do something in a 'generic' way so it can evolve if needed.
> 
> I think the definition of the 'ti,drive-dx' is somehow odd. It allows
> you to set it to 0x1234 and the DX pin will show 0x1234 when you capture
> 32bit. If you capture 16bit then it will transmit 0x12 (or 0x34?), no?
> If you have 4 channel capture then I won't speculate what will be on the
> DX pin ;)
> 
> Would not be better to say that the DX pin will be driven low or high
> during capture _and_ disable the playback support?

After some thinking, it might be still better to use the DX pin as GPIO
and either have a custom machine driver which would handle it (set low
when a capture trigger happens) or connect it in DAPM as a supply, bias
or something and ASoC would handle it automagically.

I think that would be cleaner in many ways. What do you think?

-- 
Péter