On Sat, Oct 12, 2019 at 12:57 AM Sridharan, Ranjani ranjani.sridharan@intel.com wrote:

On Fri, Oct 11, 2019 at 2:05 PM Daniel Baluta daniel.baluta@gmail.com wrote:

...

Hi Morimoto-san,

I'm really confused on what exactly is Front End and Back End.

Is FE a DAI or a DAI link or part of a DAI link?

In simple-card.c there is simple_dai_link_of_dpcm function:

struct snd_soc_dai_link_component *codecs = dai_link->codecs;

» /* BE is dummy */ » » codecs->of_node»» = NULL; » » codecs->dai_name» = "snd-soc-dummy-dai"; » » codecs->name» » = "snd-soc-dummy";

» » /* FE settings */ » » dai_link->dynamic» » = 1; » » dai_link->dpcm_merged_format» = 1;

So, from here it looks like BE/FE are components being part of the same link.

Another thing is:

asoc_simple_canonicalize_platform function where it does say:

» * DPCM BE can be no platform. » * Alloced memory will be waste, but not leak. » */ » if (!dai_link->platforms->of_node) » » dai_link->num_platforms = 0;

But I do want to create a BE with a platform. So, should I try to revert the following patch:

commit 794fcee8da3c0c8a01b08ecad1c181cb0a622868 Author: Kuninori Morimoto kuninori.morimoto.gx@renesas.com Date: Wed Jul 10 17:01:12 2019 +0900

ASoC: simple-card-utils: care no Platform for DPCM

commit 34614739988ad ("ASoC: soc-core: support dai_link with
platforms_num != 1") supports multi Platform, and
commit 9f3eb91753451 ("ASoC: simple-card-utils: consider CPU-Platform
possibility") removed no Platform from simple-card.

Multi Platform is now checking both Platform name/of_node are NULL case.
But in normal case, DPCM be doesn't have Platform.

Basically, what I want to do is: after the DAI link is created to call: snd_soc_fixup_dai_links_platform_name function to set a proper name for BE platform.

The problem is that above mentioned patch sets dai_link->num_platforms = 0; so even the name is set the platform component is not probed.

Hi Daniel, Have you looked into how SOF does it at the time the dai_link elem in topology is parsed? https://github.com/thesofproject/linux/blob/5edcfdf3907354de7a260a451ba611f2...

Is this what you are asking about?

Hi Ranjani,

Not really. Due to this patch:

Author: Kuninori Morimoto kuninori.morimoto.gx@renesas.com Date: Wed Jul 10 17:01:12 2019 +0900

ASoC: simple-card-utils: care no Platform for DPCM

I cannot probe platform component created by SOF.

Even if I set the correct name for BE's platform name because the above patch sets dai_link->num_platforms = 0 the platform component won't be probed. So, the topology won't be loaded.

I don't understand the full story here. There are these 3 patches:

(3) 794fcee8da3c ASoC: simple-card-utils: care no Platform for DPCM (2) 9f3eb9175345 ASoC: simple-card-utils: consider CPU-Platform possibility (1) 6f0437445735 ASoC: simple-card-utils: don't select unnecessary Platform

which I think they are doing as follows:

(1) Allows a DAI link to have no platform component attached. (2) There is an usecase where Platform can't be NULL. So, if platform->of_node is NULL then is set to platforms->of_node = cpus->of_node. (3) Now, the problem with patch (2) is when also cpus->of_node is NULL. In this case platforms->of_node becomes NULL. And the platforms is left unspecified (because platforms->name is also NULL). So, I think (3) is just an workaround by setting link->num_platforms the function soc_bind_dai_link will actually skip iterating over platforms.

My suggestion is that asoc_simple_canonicalize_platform should also check if platform has a name and in that case to skip zeroing dai_link->num_platforms.

Will send an RFC.

On Tue, Oct 15, 2019 at 4:15 AM Kuninori Morimoto kuninori.morimoto.gx@renesas.com wrote:

Hi Daniel

...

» /* BE is dummy */ » » codecs->of_node»» = NULL; » » codecs->dai_name» = "snd-soc-dummy-dai"; » » codecs->name» » = "snd-soc-dummy";

» » /* FE settings */ » » dai_link->dynamic» » = 1; » » dai_link->dpcm_merged_format» = 1;

Ahh, indeed... it is wrong comment. It should be /* Codec is dummy */ here. I will post fixup patch, soon.

Current simple-card is assuming

    FE: CPU-dummy
    BE: dummy-Codec

...

asoc_simple_canonicalize_platform function where it does say:

» * DPCM BE can be no platform. » * Alloced memory will be waste, but not leak. » */ » if (!dai_link->platforms->of_node) » » dai_link->num_platforms = 0;

But I do want to create a BE with a platform. So, should I try to revert the following

I see. I'm not using but someone added asoc_simple_parse_platform(). Maybe it can help you (?), but it is not called/used under DPCM case. If you can support it under DPCM, asoc_simple_canonicalize_platform() is no longer your issue ?

Yes, this would definitely help. Now I'm trying to figure out an acceptable way to create just one link with:

FE: CPU-dummy BE: dummy-Codec

Or even better just one:

BE: dummy-Codec.

Both audio-graph-card.c and simple-card.c deal with DPCM only with this conditions:

» » » /* » » » * It is DPCM » » » * if Codec port has many endpoints, » » » * or has convert-xxx property » » » */

or

» » » if (dpcm_selectable && » » » (num > 2 || » » » adata.convert_rate || adata.convert_channels))