linux-kernel - Re: [PATCH] ASoC: brcm: Add DSL/PON SoC audio driver

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Message-ID: <20200310162808.GI4106@sirena.org.uk>
Date:   Tue, 10 Mar 2020 16:28:08 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Kevin Li <kevin-ke.li@...adcom.com>
Cc:     Takashi Iwai <tiwai@...e.com>, Liam Girdwood <lgirdwood@...il.com>,
        Ray Jui <rjui@...adcom.com>, Jaroslav Kysela <perex@...ex.cz>,
        Scott Branden <sbranden@...adcom.com>,
        bcm-kernel-feedback-list@...adcom.com,
        Stephen Boyd <swboyd@...omium.org>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        alsa-devel@...a-project.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ASoC: brcm: Add DSL/PON SoC audio driver

On Tue, Mar 10, 2020 at 08:49:08AM -0700, Kevin Li wrote:

> > This is not how any of this is supposed to work, it's unlikely to work
> > well with other devices.  If the device supports both master and slave
> > operation then you should let the machine driver pick if the SoC or the
> > CODEC is master via set_fmt(), randomly varying this at runtime is not
> > going to be helpful.

> Maybe the name "master/slave" is confusing, these names come from internal
> chip signals and do not represent the state of the i2s bus master. Our SoC
> supports only master mode in the i2s bus. The Rx and Tx block each have an
> independent bit to indicate if it is generating the clock for the i2s bus.
> The i2s bus clocks need to be generated from either the Rx block or the Tx
> block, but not both.

Right, at the very least this needs to be better documented in the code.

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