| Message ID | 20220331000449.41062-4-povik+lin@cutebit.org |
|---|---|
| State | New |
| Headers | show |
| Series | None | expand |
On Fri, Apr 22, 2022 at 04:06:06PM +0200, Martin Povišer wrote: > > On 4. 4. 2022, at 14:28, Mark Brown <broonie@kernel.org> wrote: > > We need to figure out an interface for describing which CODEC/CPU > > combinations are connected to each other. I'm not seeing a great way to > > do that right now, probably some side data table is going to be needed, > > or perhaps the CPU DAI drivers can be persuaded to only have one DAI > > actually register and claim to support more channels? I'm not sure how > > a configuraiton like this is going to work at userspace level if the > > multiple CPU DAIs end up being visible... > To understand the issue better: How could the multiple CPU DAIs be > visible from userspace? If you register two separate DAIs (well, links) with the API without doing anything else the API will just expose them to userspace as two separate things with no indication that they're related. > What about this interim solution: In case of N-to-M links we put in > the most restrictive condition for checking capture/playback stream > validity: we check all of the CPU DAIs. Whatever ends up being the > proper solution later can only be less restrictive than this. That's not the issue here? > As a reminder what happens on the Macs: the platform driver drives > all the CPU-side I2S ports that belong to the link with the same data, > so the particular CPU/CODEC wiring doesn’t matter. Oh, that's not something I was aware of. In that case this is the wrong API - you should be using DPCM to map one front end onto multiple back ends (Kirkwood does something similar IIRC, there will be other examples but that's probably the simplest). The back ends probably don't really need to know that they're on the same physical bus (if indeed they are).
> On 25. 4. 2022, at 14:25, Mark Brown <broonie@kernel.org> wrote: > > On Fri, Apr 22, 2022 at 04:06:06PM +0200, Martin Povišer wrote: >>> On 4. 4. 2022, at 14:28, Mark Brown <broonie@kernel.org> wrote: > >>> We need to figure out an interface for describing which CODEC/CPU >>> combinations are connected to each other. I'm not seeing a great way to >>> do that right now, probably some side data table is going to be needed, >>> or perhaps the CPU DAI drivers can be persuaded to only have one DAI >>> actually register and claim to support more channels? I'm not sure how >>> a configuraiton like this is going to work at userspace level if the >>> multiple CPU DAIs end up being visible... > >> To understand the issue better: How could the multiple CPU DAIs be >> visible from userspace? > > If you register two separate DAIs (well, links) with the API without > doing anything else the API will just expose them to userspace as two > separate things with no indication that they're related. Sure, but what I am addressing here is a single DAI link with multiple CPU DAIs, invoked in DT like this: dai-link@0 { link-name = "Speakers"; mclk-fs = <256>; cpu { sound-dai = <&mca 0>, <&mca 1>; }; codec { sound-dai = <&speaker_left_woof1>, <&speaker_right_woof1>, <&speaker_left_tweet>, <&speaker_right_tweet>, <&speaker_left_woof2>, <&speaker_right_woof2>; }; }; >> What about this interim solution: In case of N-to-M links we put in >> the most restrictive condition for checking capture/playback stream >> validity: we check all of the CPU DAIs. Whatever ends up being the >> proper solution later can only be less restrictive than this. > > That's not the issue here? Well to me it looks like it is. Because if I invoke the DAI link like I quoted above, and the platform driver supports it, the playback/capture stream validity check is the only place it breaks down. Notwithstanding this may be the wrong API as you wrote. >> As a reminder what happens on the Macs: the platform driver drives >> all the CPU-side I2S ports that belong to the link with the same data, >> so the particular CPU/CODEC wiring doesn’t matter. > > Oh, that's not something I was aware of. In that case this is the wrong > API - you should be using DPCM to map one front end onto multiple back > ends (Kirkwood does something similar IIRC, there will be other examples > but that's probably the simplest). The back ends probably don't really > need to know that they're on the same physical bus (if indeed they are). I guess I need to look into that.
On Mon, Apr 25, 2022 at 02:34:33PM +0200, Martin Povišer wrote: > > On 25. 4. 2022, at 14:25, Mark Brown <broonie@kernel.org> wrote: > > If you register two separate DAIs (well, links) with the API without > > doing anything else the API will just expose them to userspace as two > > separate things with no indication that they're related. > Sure, but what I am addressing here is a single DAI link with multiple > CPU DAIs, invoked in DT like this: > dai-link@0 { > link-name = "Speakers"; > mclk-fs = <256>; > > cpu { > sound-dai = <&mca 0>, <&mca 1>; > }; > codec { > sound-dai = <&speaker_left_woof1>, > <&speaker_right_woof1>, > <&speaker_left_tweet>, > <&speaker_right_tweet>, > <&speaker_left_woof2>, > <&speaker_right_woof2>; > }; > }; You could parse this into two separate links for the benefit of the framewokr if you're using a custom machine driver (which I suspect you probably have to). > >> What about this interim solution: In case of N-to-M links we put in > >> the most restrictive condition for checking capture/playback stream > >> validity: we check all of the CPU DAIs. Whatever ends up being the > >> proper solution later can only be less restrictive than this. > > That's not the issue here? > Well to me it looks like it is. Because if I invoke the DAI link like > I quoted above, and the platform driver supports it, the playback/capture > stream validity check is the only place it breaks down. Notwithstanding > this may be the wrong API as you wrote. I am surprised that doesn't otherwise explode TBH - at the very least I'd expect it to show two PCMs to userspace which if I'm understanding your description correctly isn't really what's going on.
> On 25. 4. 2022, at 14:55, Mark Brown <broonie@kernel.org> wrote: > > On Mon, Apr 25, 2022 at 02:34:33PM +0200, Martin Povišer wrote: >>> On 25. 4. 2022, at 14:25, Mark Brown <broonie@kernel.org> wrote: > >>> If you register two separate DAIs (well, links) with the API without >>> doing anything else the API will just expose them to userspace as two >>> separate things with no indication that they're related. > >> Sure, but what I am addressing here is a single DAI link with multiple >> CPU DAIs, invoked in DT like this: > >> dai-link@0 { >> link-name = "Speakers"; >> mclk-fs = <256>; >> >> cpu { >> sound-dai = <&mca 0>, <&mca 1>; >> }; >> codec { >> sound-dai = <&speaker_left_woof1>, >> <&speaker_right_woof1>, >> <&speaker_left_tweet>, >> <&speaker_right_tweet>, >> <&speaker_left_woof2>, >> <&speaker_right_woof2>; >> }; >> }; > > You could parse this into two separate links for the benefit of the > framewokr if you're using a custom machine driver (which I suspect you > probably have to). Yeah, this is parsed by the ‘macaudio’ machine driver from the series. >>>> What about this interim solution: In case of N-to-M links we put in >>>> the most restrictive condition for checking capture/playback stream >>>> validity: we check all of the CPU DAIs. Whatever ends up being the >>>> proper solution later can only be less restrictive than this. > >>> That's not the issue here? > >> Well to me it looks like it is. Because if I invoke the DAI link like >> I quoted above, and the platform driver supports it, the playback/capture >> stream validity check is the only place it breaks down. Notwithstanding >> this may be the wrong API as you wrote. > > I am surprised that doesn't otherwise explode TBH - at the very least > I'd expect it to show two PCMs to userspace which if I'm understanding > your description correctly isn't really what's going on. I fill in a single snd_soc_dai_link, it exposes a single PCM and works like a charm. That is as long as I patch the playback/capture check in question. I read that to be the clear intention of ASoC code: a DAI link becomes one snd_soc_pcm_runtime.
> On 25. 4. 2022, at 15:46, Mark Brown <broonie@kernel.org> wrote: > > On Mon, Apr 25, 2022 at 03:11:14PM +0200, Martin Povišer wrote: >>> On 25. 4. 2022, at 14:55, Mark Brown <broonie@kernel.org> wrote: > >>> I am surprised that doesn't otherwise explode TBH - at the very least >>> I'd expect it to show two PCMs to userspace which if I'm understanding >>> your description correctly isn't really what's going on. > >> I fill in a single snd_soc_dai_link, it exposes a single PCM and works >> like a charm. That is as long as I patch the playback/capture check in >> question. > >> I read that to be the clear intention of ASoC code: a DAI link becomes >> one snd_soc_pcm_runtime. > > Yes, so long as you boil it down to a single link it works fine but the > bit on top of the binding where you tie the two CPU DAIs to what is > actually exposed is all in code. The reason this stuff isn't filled in > is that connecting the thing that applications see to the physical links > isn't at all obvious and needs at least some driver sitting in the > middle to make the links - I'd imagine there's a DSP sitting there which > probably has quite a bit of flexability about how the various hardware > components available are actually related. This makes figuring out what > to do with the relationship between the multiple CPU DAIs hard. I get the gist. Anyway unless you tell me otherwise I will assume I need to move to DPCM with the platform/machine driver.
diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c index 9a954680d492..770cf367a147 100644 --- a/sound/soc/soc-pcm.c +++ b/sound/soc/soc-pcm.c @@ -2781,9 +2781,12 @@ static int soc_get_playback_capture(struct snd_soc_pcm_runtime *rtd, } else if (rtd->num_cpus == rtd->num_codecs) { cpu_dai = asoc_rtd_to_cpu(rtd, i); } else { +#if 0 dev_err(rtd->card->dev, "N cpus to M codecs link is not supported yet\n"); return -EINVAL; +#endif + cpu_dai = asoc_rtd_to_cpu(rtd, 0); } if (snd_soc_dai_stream_valid(codec_dai, SNDRV_PCM_STREAM_PLAYBACK) &&
Tolerate N-to-M DAI links while using the first CPU DAI to decide playback/capture abilities. Signed-off-by: Martin Povišer <povik+lin@cutebit.org> --- sound/soc/soc-pcm.c | 3 +++ 1 file changed, 3 insertions(+)