linux-kernel - Re: [PATCH v2] ASoC: dt-bindings: simple-card: add triggers properties

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Message-ID: <78fdef90-6841-b7c6-198b-5902cdc06298@inbox.ru>
Date:   Wed, 19 Jul 2023 10:13:07 +0300
From:   Maxim Kochetkov <fido_max@...ox.ru>
To:     Rob Herring <robh@...nel.org>
Cc:     alsa-devel@...a-project.org, Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        Sameer Pujar <spujar@...dia.com>,
        Astrid Rost <astrid.rost@...s.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Herve Codina <herve.codina@...tlin.com>,
        Aidan MacDonald <aidanmacdonald.0x0@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ASoC: dt-bindings: simple-card: add triggers
 properties



On 19.07.2023 01:08, Rob Herring wrote:
> On Sat, Jul 15, 2023 at 11:30:43AM +0300, Maxim Kochetkov wrote:
>> The trigger-start/stop properties allows to specify DAI link
>> trigger ordering method.
> 
> Obviously. Why do you need these? What problem does it solve?

It allows using simple card for some DMA-based CPU component which 
requires different start/stop sequence (stop DMA before CPU component, 
start DMA after CPU component).
There are a lot of boards which have no audio codec on board. It has 
only I2S/TDM/etc... and you can attach any external codec on its pins. 
It looks like simple audio card is enough for this cases. It is much 
better than to copy-paste simple audio card code to the new custom 
driver with new combination of CPU/codec.

> 
> I don't think these belong in simple-card. What's next? What if you need
> delays between each step? This is the problem with 'simple' or 'generic'
> bindings. It's a never ending addition of properties which are not well
> thought out.

Can you please suggest the better way to specify start/stop trigger 
order via DT?

>> +  trigger-start:
>> +    description: |-
>> +      Start trigger ordering method:
>> +      default: Link->Component->DAI
>> +      ldc: Link->DAI->Component
>> +    $ref: /schemas/types.yaml#/definitions/string
>> +    items:
>> +      enum:
>> +        - default
> 
> Why do you need a value of 'default'? What's the default when the
> property is not present?
It comes from
enum snd_soc_trigger_order {
	SND_SOC_TRIGGER_ORDER_DEFAULT	= 0,	
	SND_SOC_TRIGGER_ORDER_LDC,		
	SND_SOC_TRIGGER_ORDER_MAX,
};
default value is 0 (SND_SOC_TRIGGER_ORDER_DEFAULT)

>>     format:
>>       description: audio format.
>>       items:
>> @@ -210,6 +232,10 @@ properties:
>>       maxItems: 1
>>     simple-audio-card,mic-det-gpio:
>>       maxItems: 1
>> +  simple-audio-card,trigger-start:
>> +    $ref: "#/definitions/trigger-start"
>> +  simple-audio-card,trigger-stop:
>> +    $ref: "#/definitions/trigger-stop"
> 
> Don't continue this 'simple-audio-card,' prefix pattern. With it, no
> other binding can use these properties.

Ok.

> 
>>   
>>   patternProperties:
>>     "^simple-audio-card,cpu(@[0-9a-f]+)?$":
>> @@ -259,6 +285,11 @@ patternProperties:
>>           maxItems: 1
>>         mic-det-gpio:
>>           maxItems: 1
>> +      trigger-start:
>> +        $ref: "#/definitions/trigger-start"
>> +      trigger-stop:
>> +        $ref: "#/definitions/trigger-stop"
>> +

Should I keep only this section?