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Date:   Mon, 2 Sep 2019 16:52:18 +0100
From:   Mark Brown <broonie@kernel.org>
To:     Daniel Baluta <daniel.baluta@gmail.com>
Cc:     Daniel Baluta <daniel.baluta@nxp.com>,
        Fabio Estevam <festevam@gmail.com>,
        Nicolin Chen <nicoleotsuka@gmail.com>,
        Xiubo Li <Xiubo.Lee@gmail.com>,
        "S.j. Wang" <shengjiu.wang@nxp.com>,
        Linux-ALSA <alsa-devel@alsa-project.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Timur Tabi <timur@kernel.org>,
        Cosmin-Gabriel Samoila <gabrielcsmo@gmail.com>,
        NXP Linux Team <linux-imx@nxp.com>,
        Cosmin-Gabriel Samoila <cosmin.samoila@nxp.com>
Subject: Re: [PATCH] ASoC: fsl_sai: Set SAI Channel Mode to Output Mode
Message-ID: <20190902155218.GC5819@sirena.co.uk>
References: <20190830225514.5283-1-daniel.baluta@nxp.com>
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On Mon, Sep 02, 2019 at 04:35:56PM +0300, Daniel Baluta wrote:
> On Mon, Sep 2, 2019 at 3:42 PM Mark Brown <broonie@kernel.org> wrote:

> > This patch seems to do this unconditionally.  This is fine for
> > configurations where the SoC is the only thing driving the bus but will
> > mean that for TDM configurations where something else also drives some
> > of the slots we'll end up with both devices driving simultaneously.  The
> > safest thing would be to set this only if TDM isn't configured.

> I thought that the SAI IP is the single owner of the audio data lines,
> so even in TDM
> mode SAI IP (which is inside SoC) is the only one adding data on the bus.

> Now, you say that there could be two devices driving some of he masked
> slots right?

Doing that is the major point of TDM modes.  It could even be another
SAI on the same bus.

> I'm not sure how to really figure out that SAI is running in TDM mode.

As a first approximation you could just check if set_tdm_slots() has
been called, it might still be the only device but it's a good first
guess.

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