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Date:   Fri, 18 Dec 2020 09:50:01 +0000
From:   Charles Keepax <ckeepax@opensource.cirrus.com>
To:     Jerome Brunet <jbrunet@baylibre.com>
CC:     Mark Brown <broonie@kernel.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        <alsa-devel@alsa-project.org>, <linux-kernel@vger.kernel.org>,
        <linux-amlogic@lists.infradead.org>,
        Kevin Hilman <khilman@baylibre.com>
Subject: Re: [PATCH] ASoC: meson: axg-tdm-interface: fix loopback
Message-ID: <20201218095001.GF9673@ediswmail.ad.cirrus.com>
References: <20201217150812.3247405-1-jbrunet@baylibre.com>
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On Thu, Dec 17, 2020 at 04:08:12PM +0100, Jerome Brunet wrote:
> When the axg-tdm-interface was introduced, the backend DAI was marked as an
> endpoint when DPCM was walking the DAPM graph to find a its BE.
> 
> It is no longer the case since this
> commit 8dd26dff00c0 ("ASoC: dapm: Fix handling of custom_stop_condition on DAPM graph walks")
> Because of this, when DPCM finds a BE it does everything it needs on the
> DAIs but it won't power up the widgets between the FE and the BE if there
> is no actual endpoint after the BE.
> 
> On meson-axg HWs, the loopback is a special DAI of the tdm-interface BE.
> It is only linked to the dummy codec since there no actual HW after it.
> >From the DAPM perspective, the DAI has no endpoint. Because of this, the TDM
> decoder, which is a widget between the FE and BE is not powered up.
> 
> >From the user perspective, everything seems fine but no data is produced.
> 
> Connecting the Loopback DAI to a dummy DAPM endpoint solves the problem.
> 
> Fixes: 8dd26dff00c0 ("ASoC: dapm: Fix handling of custom_stop_condition on DAPM graph walks")
> Cc: Charles Keepax <ckeepax@opensource.cirrus.com>
> Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
> ---

Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>

Thanks,
Charles