linux-kernel - Re: [PATCH 2/2] ASoC: Adds support for TAS575x to the pcm512x driver

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Message-ID: <bb3e5ccf-6eb5-4a36-9af0-b33f2db68445@sirena.org.uk>
Date:   Thu, 7 Sep 2023 17:28:30 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Joerg Schambacher <joerg.hifiberry@...il.com>
Cc:     a-krasser@...com, joerg@...iberry.com,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Zhang Qilong <zhangqilong3@...wei.com>,
        alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] ASoC: Adds support for TAS575x to the pcm512x driver

On Thu, Sep 07, 2023 at 06:21:50PM +0200, Joerg Schambacher wrote:

> And yes, we cannot be sure that future devices may require different
> settings, but I can hardly imagine anything completely different than
> this approach with the usual audio MCLK frequencies.

They may for example be restricted and just not the the incoming MCLK
divider, or require a higher frequency for some fancy processing.  In
any case tas_device is just an obviously bad name here - there should be
a flag per quirk, not a flag per entire class of devices.

> > This is probably a separate quirk?  I'm a bit concerned about what's
> > turning the PLL off here...

> The PLL should not be used in this specific case where all divisions are
> just divide-by-2's. Your original code does reflect that and turns the
> PLL off. It improves jitter and finally audio performance.

> But in the case of the TAS-devices we even then need the PLL to
> drive the AMP clocks.

That's definitely a separate quirk, and does sound like it should be
driven from the bias management or DAPM more than hw_params.

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