linux-kernel - Re: [PATCH 0/4] ASoC: fsl_asrc: allow selecting arbitrary clocks

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Message-ID: <0a56326b-27a9-d9f4-3923-8773963d7548@collabora.com>
Date:   Wed, 15 Jul 2020 18:18:38 +0200
From:   Arnaud Ferraris <arnaud.ferraris@...labora.com>
To:     Mark Brown <broonie@...nel.org>,
        Nicolin Chen <nicoleotsuka@...il.com>
Cc:     alsa-devel@...a-project.org, Timur Tabi <timur@...nel.org>,
        Xiubo Li <Xiubo.Lee@...il.com>, linux-kernel@...r.kernel.org,
        Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Rob Herring <robh+dt@...nel.org>, kernel@...labora.com,
        Fabio Estevam <festevam@...il.com>
Subject: Re: [PATCH 0/4] ASoC: fsl_asrc: allow selecting arbitrary clocks

Hi,

Le 15/07/2020 à 16:05, Mark Brown a écrit :
> 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