linux-kernel - Re: [PATCH v4 10/23] ASoC: simple-card: Wrong daifmt for CPU end of DPCM DAI link

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Date:   30 Jun 2020 09:56:17 +0900
From:   Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>
To:     Sameer Pujar <spujar@...dia.com>
Cc:     <broonie@...nel.org>, <perex@...ex.cz>, <tiwai@...e.com>,
        <robh+dt@...nel.org>, <lgirdwood@...il.com>,
        <thierry.reding@...il.com>, <jonathanh@...dia.com>,
        <digetx@...il.com>, <alsa-devel@...a-project.org>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <sharadg@...dia.com>, <mkumard@...dia.com>,
        <viswanathl@...dia.com>, <rlokhande@...dia.com>,
        <dramesh@...dia.com>, <atalambedu@...dia.com>,
        <nwartikar@...dia.com>, <swarren@...dia.com>,
        <nicoleotsuka@...il.com>
Subject: Re: [PATCH v4 10/23] ASoC: simple-card: Wrong daifmt for CPU end of DPCM DAI link


Hi Sameer

>  snd_soc_runtime_set_dai_fmt() {
>      ...
> 
>      if (cpu_dai->component->driver->non_legacy_dai_naming)
>          fmt = inv_dai_fmt;
> 
>      ...
>  }
> 
> Above flips polarity for 'cpu_dai' if 'non_legacy_dai_naming' flag is set.
> 
> 1. Hence example mentioned in the commit message does not work if my 'cpu_dai'
> driver does not have this flag set.

?
Do you want fo flip it ? or don't flip?
It is for Codec <-> Codec connection.

> 2. While it is true that we consider reference of 'Codec' mode for simple CPU<->
> Codec DAI links, for DPCM this does not seem flexible. For DPCM links CPU and
> Codec are not directly connected (CPU<->Dummy or Dummy<->Codec). Please
> consider, for example, if the DAI link has multiple CPU/Codecs. Which 'Codec'
> reference needs to be considered? Isn't it better if we explicitly mention which
> DAI we want to operate as 'Master'?

I think Lars-Peter has (had ?) plan for this SND_SOC_DAIFMT_CBx_CFx
flag flexibility ? Yes maybe it is needed for multi CPU/Codec system.

Thank you for your help !!

Best regards
---
Kuninori Morimoto