Re: [PATCH 1/4] ASoC: dt-bindings: document new symmetric-clock-role flag

From: "Alvin Šipraga" <ALSI@bang-olufsen.dk>
To: Mark Brown <broonie@kernel.org>
Cc: "Alvin Šipraga" <alvin@pqrs.dk>,
	"Liam Girdwood" <lgirdwood@gmail.com>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
	"Conor Dooley" <conor+dt@kernel.org>,
	"Jaroslav Kysela" <perex@perex.cz>,
	"Takashi Iwai" <tiwai@suse.com>,
	"Kuninori Morimoto" <kuninori.morimoto.gx@renesas.com>,
	"alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/4] ASoC: dt-bindings: document new symmetric-clock-role flag
Date: Mon, 5 Jun 2023 11:42:44 +0000	[thread overview]
Message-ID: <epx43xeghpqcourix74uyjdm6kpovlqocx7l34z3bvumk7ehfb@sfvjvladp2oh> (raw)
In-Reply-To: <91b6d02a-25d5-4835-942e-3f8072bd8897@sirena.org.uk>

On Fri, Jun 02, 2023 at 01:19:08PM +0100, Mark Brown wrote:
> On Fri, Jun 02, 2023 at 12:12:52PM +0000, Alvin Šipraga wrote:
> > On Fri, Jun 02, 2023 at 12:43:51PM +0100, Mark Brown wrote:
> 
> > > Why would we have a property for this and not just describe whatever the
> > > actual clocking arrangement is?
> 
> > Sure - let me just elaborate on my thinking and maybe you can help me with a
> > better approach:
> 
> > The clocking arrangement is encoded in the dai_fmt field of snd_soc_dai_link,
> > but this is a single value that describes the format on both ends. The current
> > behaviour of ASoC is to flip the clock roles encoded in dai_fmt when applying it
> > to the CPU side of the link.
> 
> > Looking from a DT perspective, if I do not specify e.g. bitclock-master on
> > either side of the link, then the dai_fmt will describe the codec as a bitclock
> > consumer and (after flipping) the CPU as a provider. That's the default
> > implication of the DT bindings and I can't break compatibility there.
> 
> None of this addresses my question.  To repeat why would we not just
> describe the actual clocking arrangement here - this property does not
> specify where the clock actually comes from at all, we're still going to
> need additional information for that and if we've described that clock
> then we already know it's there without having to specify any more
> properties.

Maybe I overcomplicated your point with my previous reply. Some questions to
clarify:

1. You don't like the DT property because it should be inferrable by other
means. Correct?

2. As for the flag added to snd_soc_dai_link, do you think that is an OK
approach?

Just want to understand which direction you would like me to focus the
effort.

Kind regards,
Alvin