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Date:   Fri, 14 Feb 2020 14:04:28 +0100
From:   Sebastian Reichel <sre@kernel.org>
To:     Tony Lindgren <tony@atomide.com>
Cc:     Peter Ujfalusi <peter.ujfalusi@ti.com>,
        Mark Brown <broonie@kernel.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Jaroslav Kysela <perex@perex.cz>,
        Takashi Iwai <tiwai@suse.com>, alsa-devel@alsa-project.org,
        linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org,
        Aaro Koskinen <aaro.koskinen@iki.fi>,
        "Arthur D ." <spinal.by@gmail.com>,
        Jarkko Nikula <jarkko.nikula@bitmer.com>,
        Merlijn Wajer <merlijn@wizzup.org>, Pavel Machek <pavel@ucw.cz>
Subject: Re: [PATCH] ASoC: ti: Allocate dais dynamically for TDM and audio
 graph card
Message-ID: <20200214130428.gkhmr55ptmi2bh2x@earth.universe>
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Hi,

On Thu, Feb 13, 2020 at 05:34:54PM -0800, Tony Lindgren wrote:
> * Sebastian Reichel <sre@kernel.org> [200214 00:35]:
> > On Wed, Feb 12, 2020 at 06:35:43AM -0800, Tony Lindgren wrote:
> > > Yes this should follow the audio-graph-card.txt example. We end up wi=
th
> > > mcbsp3 dts node as below on droid4:
> > >=20
> > > &mcbsp3 {
> > >         #sound-dai-cells =3D <0>;
> > >         pinctrl-names =3D "default";
> > >         pinctrl-0 =3D <&mcbsp3_pins>;
> > >         status =3D "okay";
> > >=20
> > >         ports {
> > >                 mcbsp3_port: port@0 {
> > >                         #address-cells =3D <1>;
> > >                         #size-cells =3D <0>;
> > >=20
> > >                         cpu_dai3: endpoint@0 {
> >=20
> > cpu_dai3_cpcap
> >=20
> > >                                 reg =3D <0>;
> > >                                 dai-format =3D "dsp_a";
> > >                                 frame-master =3D <&cpcap_audio_codec1=
>;
> > >                                 bitclock-master =3D <&cpcap_audio_cod=
ec1>;
> > >                                 remote-endpoint =3D <&cpcap_audio_cod=
ec1>;
> > >                         };
> > >=20
> > >                         cpu_dai_mdm: endpoint@1 {
> >=20
> > cpu_dai3_mdm
>=20
> OK
>=20
> > >                                 reg =3D <1>;
> > >                                 dai-format =3D "dsp_a";
> > >                                 frame-master =3D <&cpcap_audio_codec1=
>;
> > >                                 bitclock-master =3D <&cpcap_audio_cod=
ec1>;
> > >                                 remote-endpoint =3D <&mot_mdm6600_aud=
io_codec0>;
> > >                         };
> > >                 };
> > >         };
> > > };
> > >=20
> > > That is pretty much the same as the 'Multi DAI with DPCM' example, wi=
th
> > > dne dai, and multiple endpoints. I think we still have just one port
> > > for one i2s transport on the mcbsp :)
> > >=20
> > > Does the above look as what you would expect based on the binding?
> >=20
> > I haven't had a look at this for quite some time. I suppose the
> > cpcap voice DAI and the modem will also have two endpoints? So
> > once the BT support is added it will looks like this [simplified]?
>=20
> Well it will be even simpler, no need for extra endpoints at
> the codecs, see below.
> =20
> > &mcbsp3 {
> >     ports {
> >         port@0 {
> >             cpu_dai3_cpcap: endpoint@0 {};
> >             cpu_dai3_modem: endpoint@1 {};
> >             cpu_dai3_bt: endpoint@2 {};
> >         };
> >     };
> > };
>=20
> But yes, bluetooth would be just added as above under mcbsp3.
>=20
[...]
>
> Then the modem codec looks like this:
>=20
> mot_mdm6600_audio: audio-codec {
> 	#address-cells =3D <1>;
> 	#size-cells =3D <0>;
> 	#sound-dai-cells =3D <1>;
>=20
> 	port@0 {
> 		mot_mdm6600_audio_codec0: endpoint {
> 			remote-endpoint =3D <&cpu_dai_mdm>;
> 		};
> 	};
> };
>=20
> > &bluetooth {
> >     ports {
> >         port@0 {
> >             bt_dai_cpu: endpoint@0 {};
> >             bt_dai_modem: endpoint@1 {};
> >             bt_dai_cpcap: endpoint@2 {};
> >         };
> >     };
> > };
>=20
> And bluetooth would be similar to cpcap_audio and mot_mdm6600_audio
> above.

My understanding is, that CPU is not involved for calls (except for
setting up cpcap registers correctly). Basically McBSP3 should
remain idle for a call and data goes directly from modem to cpcap.
The same should work for modem <-> BT, except that CPCAP seems to
always provide the clock. That would imply a direct link between
modem and codec / BT?

> My guess is that only cpcap registers and clock rate needs to be
> changed for bluetooth audio BTW, so if somebody havs a bluetooth
> headset just do the following in Android:
>=20
> # cpcaprw --all > /tmp/before
> configure bluetooth headset for audio in android and start
> playing some music or make a phone call
> ...
> # cpcaprw --all > /tmp/after
> stop playing music or phone call
> ...
> diff -u /tmp/before /tmp/after
>=20
> The registers will be different for a bluetooth phone call and
> playing music.

I can provider register values once I find some time.

-- Sebastian

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