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Subject: Re: [PATCH 0/4] ASoC: fsl_asrc: allow selecting arbitrary clocks
To:     Mark Brown <broonie@kernel.org>,
        Nicolin Chen <nicoleotsuka@gmail.com>
Cc:     alsa-devel@alsa-project.org, Timur Tabi <timur@kernel.org>,
        Xiubo Li <Xiubo.Lee@gmail.com>, linux-kernel@vger.kernel.org,
        Takashi Iwai <tiwai@suse.com>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Rob Herring <robh+dt@kernel.org>, kernel@collabora.com,
        Fabio Estevam <festevam@gmail.com>
References: <20200702142235.235869-1-arnaud.ferraris@collabora.com>
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 <20200714201544.GA10501@Asurada-Nvidia> <20200714202753.GM4900@sirena.org.uk>
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From:   Arnaud Ferraris <arnaud.ferraris@collabora.com>
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Date:   Wed, 15 Jul 2020 18:18:38 +0200
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Hi,

Le 15/07/2020 ? 16:05, Mark Brown a ?crit?:
> On Tue, Jul 14, 2020 at 01:50:50PM -0700, Nicolin Chen wrote:
> Anything wrong with ASRC selecting SSI1 clock for both cases? The
> driver calculates the divisors based on the given clock rate, so
> the final internal rate should be the same. If there's a problem,
> I feel that's a separate bug.

Calculations are indeed good, but then the clock selection setting in
the ASRCSR register would also use SSI1 as the input clock, which
doesn't work in our case.

>> On Tue, Jul 14, 2020 at 09:27:53PM +0100, Mark Brown wrote:
> 
> If you've got two radios that both need to sync to some radio derived
> frequency it gets a bit more entertaining.

It was indeed a fun ride trying to make it work for all the use-cases we
were targetting.

> 
>> Yet, in case that we need to support such an edge case, what's
>> a relatively common practice to allow system select the clock
>> source now?
> 
> Honestly for anything that fun it tends to be a custom machine driver.
> A property would seem reasonable though.

I think so, does my initial implementation of the properties look
sensible to you? ("fsl,asrc-input-clock" & "fsl,asrc-output-clock")

Regards,
Arnaud