How to select input from muxer in front of SSI on i.MX6

How to select input from muxer in front of SSI on i.MX6

[Jean-Michel Hautbois]

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Hi,

I am now working on making my audio path working completely.
And I get some difficulties to write a DT for my needs.
I join a picture which is not the reality but a simplified version of the board.

I have a FPGA between my codecs and my i.MX6. This FPGA is responsible
of lots of things, and in particular of muxing signals.
I can program it in order to get the audio signal I want on the SSI I
want (so sgtl5000 can ben on SSI1 or SSI2 or both). This path is not a
single codec, but a multiple codec one.
So I can have on SSI1 LineIn from sgtl5000 or audio from hdmi (adv7611).

I don't know how to write it in DT, regarding audmux for instance, and
the sound{} node...
And I don't know how to drive all these peripherals (from arecord, I
wish I have hw:0,0 is LineIn, hw:0;1 is HDMI, etc.).

Any help would be appreciated :).
Thanks,
JM

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Re: How to select input from muxer in front of SSI on i.MX6

[Nicolin Chen]

CCed Mark and Liam.

On Fri, Sep 19, 2014 at 05:18:08PM +0200, Jean-Michel Hautbois wrote:
> Hi,
> 
> I am now working on making my audio path working completely.
> And I get some difficulties to write a DT for my needs.
> I join a picture which is not the reality but a simplified version of the board.
> 
> I have a FPGA between my codecs and my i.MX6. This FPGA is responsible
> of lots of things, and in particular of muxing signals.
> I can program it in order to get the audio signal I want on the SSI I
> want (so sgtl5000 can ben on SSI1 or SSI2 or both). This path is not a
> single codec, but a multiple codec one.
> So I can have on SSI1 LineIn from sgtl5000 or audio from hdmi (adv7611).
> 
> I don't know how to write it in DT, regarding audmux for instance, and
> the sound{} node...
> And I don't know how to drive all these peripherals (from arecord, I
> wish I have hw:0,0 is LineIn, hw:0;1 is HDMI, etc.).

This looks like a DPCM (Documentation/sound/alsa/soc/DPCM.txt) to me.

I'm not sure how to write a DT for DPCM either. But it seems that you
might need a specific machine driver (guessing).

I saw Morimoto-san plans to add DPCM into Simple Card, but not sure
when they will finish it. Otherwise, you may use Simple Card while
following their defined DT formats.

Nicolin

Re: How to select input from muxer in front of SSI on i.MX6

[Jean-Michel Hautbois]

Hi,

2014-09-19 19:52 GMT+02:00 Nicolin Chen <nicoleotsuka@gmail.com>:
> CCed Mark and Liam.
>
> On Fri, Sep 19, 2014 at 05:18:08PM +0200, Jean-Michel Hautbois wrote:
>> Hi,
>>
>> I am now working on making my audio path working completely.
>> And I get some difficulties to write a DT for my needs.
>> I join a picture which is not the reality but a simplified version of the board.
>>
>> I have a FPGA between my codecs and my i.MX6. This FPGA is responsible
>> of lots of things, and in particular of muxing signals.
>> I can program it in order to get the audio signal I want on the SSI I
>> want (so sgtl5000 can ben on SSI1 or SSI2 or both). This path is not a
>> single codec, but a multiple codec one.
>> So I can have on SSI1 LineIn from sgtl5000 or audio from hdmi (adv7611).
>>
>> I don't know how to write it in DT, regarding audmux for instance, and
>> the sound{} node...
>> And I don't know how to drive all these peripherals (from arecord, I
>> wish I have hw:0,0 is LineIn, hw:0;1 is HDMI, etc.).
>
> This looks like a DPCM (Documentation/sound/alsa/soc/DPCM.txt) to me.
>
> I'm not sure how to write a DT for DPCM either. But it seems that you
> might need a specific machine driver (guessing).
>
> I saw Morimoto-san plans to add DPCM into Simple Card, but not sure
> when they will finish it. Otherwise, you may use Simple Card while
> following their defined DT formats.

Thanks, that's interesting. It looks like a DPCM, but in the other
order (from FE to BE). I probably need a new driver, you are right.
But I still don't know how/what I should declare in the DT...

Thanks,
JM

Re: How to select input from muxer in front of SSI on i.MX6

[Mark Brown]

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On Fri, Sep 19, 2014 at 10:52:06AM -0700, Nicolin Chen wrote:

> This looks like a DPCM (Documentation/sound/alsa/soc/DPCM.txt) to me.

> I'm not sure how to write a DT for DPCM either. But it seems that you
> might need a specific machine driver (guessing).

> I saw Morimoto-san plans to add DPCM into Simple Card, but not sure
> when they will finish it. Otherwise, you may use Simple Card while
> following their defined DT formats.

Depending on what the system looks like it's not at all clear that there
should be any visibility at all of DPCM in the DT - it's a detail of how
Linux is implemented at the end of the day.

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Re: How to select input from muxer in front of SSI on i.MX6

[Jean-Michel Hautbois]

Le 23 sept. 2014 03:51, "Mark Brown" <broonie@kernel.org> a écrit :
>
> On Fri, Sep 19, 2014 at 10:52:06AM -0700, Nicolin Chen wrote:
>
> > This looks like a DPCM (Documentation/sound/alsa/soc/DPCM.txt) to me.
>
> > I'm not sure how to write a DT for DPCM either. But it seems that you
> > might need a specific machine driver (guessing).
>
> > I saw Morimoto-san plans to add DPCM into Simple Card, but not sure
> > when they will finish it. Otherwise, you may use Simple Card while
> > following their defined DT formats.
>
> Depending on what the system looks like it's not at all clear that there
> should be any visibility at all of DPCM in the DT - it's a detail of how
> Linux is implemented at the end of the day.

So this should definitely be implemented directly in a specific driver for
my FPGA which is a DPCM right ?

Thanks,
JM
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Re: How to select input from muxer in front of SSI on i.MX6

[Mark Brown]

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On Tue, Sep 23, 2014 at 08:11:27AM +0200, Jean-Michel Hautbois wrote:
> Le 23 sept. 2014 03:51, "Mark Brown" <broonie@kernel.org> a écrit :

> > Depending on what the system looks like it's not at all clear that there
> > should be any visibility at all of DPCM in the DT - it's a detail of how
> > Linux is implemented at the end of the day.

> So this should definitely be implemented directly in a specific driver for
> my FPGA which is a DPCM right ?

No, that's really not what DPCM is all about...  if this is a physically
separate device that's not got direct memory access it's probably more
appropriate to represent as a CODEC.  I was CCed in part way so don't
entirely know.

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Re: How to select input from muxer in front of SSI on i.MX6

[Jean-Michel Hautbois]

Hi Mark,

2014-09-24 10:21 GMT+02:00 Mark Brown <broonie@kernel.org>:
> On Tue, Sep 23, 2014 at 08:11:27AM +0200, Jean-Michel Hautbois wrote:
>> Le 23 sept. 2014 03:51, "Mark Brown" <broonie@kernel.org> a écrit :
>
>> > Depending on what the system looks like it's not at all clear that there
>> > should be any visibility at all of DPCM in the DT - it's a detail of how
>> > Linux is implemented at the end of the day.
>
>> So this should definitely be implemented directly in a specific driver for
>> my FPGA which is a DPCM right ?
>
> No, that's really not what DPCM is all about...  if this is a physically
> separate device that's not got direct memory access it's probably more
> appropriate to represent as a CODEC.  I was CCed in part way so don't
> entirely know.

OK, sorry for my late answer, but I was on a lot of things at the same time :/.
Well, here is a tentative to explain what I want to do :
http://paste.kde.org/pwijzty2p
The objective is to develop the "Mux I²S" part, as this is in fact a
FPGA with I²C registers which tell which input should go on which
output.

I am reading Alsa docs, in order to fully understand what should be
done, but it seems that this is nothing more than a simple codec with
no effect on audio parameters... It should be visible in alsa mixer
though, in order to drive the inputs from user space easily.

I hope this is clearer...
Thanks !
JM
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Re: How to select input from muxer in front of SSI on i.MX6

[Mark Brown]

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On Wed, Oct 08, 2014 at 05:24:49PM +0200, Jean-Michel Hautbois wrote:
> 2014-09-24 10:21 GMT+02:00 Mark Brown <broonie@kernel.org>:

> > No, that's really not what DPCM is all about...  if this is a physically
> > separate device that's not got direct memory access it's probably more
> > appropriate to represent as a CODEC.  I was CCed in part way so don't
> > entirely know.

> OK, sorry for my late answer, but I was on a lot of things at the same time :/.
> Well, here is a tentative to explain what I want to do :
> http://paste.kde.org/pwijzty2p
> The objective is to develop the "Mux I²S" part, as this is in fact a
> FPGA with I²C registers which tell which input should go on which
> output.

OK, this probably does fit best with DPCM at this point of view as it is
such a simple straight through connection.  At least it's probably the
lowest impedence way of doing things right now, it's not really what we
want to do longer term though.

> I am reading Alsa docs, in order to fully understand what should be
> done, but it seems that this is nothing more than a simple codec with
> no effect on audio parameters... It should be visible in alsa mixer
> though, in order to drive the inputs from user space easily.

Even a dumb CODEC at least has the effect of limitng the configurations
that can be used.

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