Re: meson-aiu: HDMI codec .prepare() callback not called

[Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>]

Hi Jerome,

On Mon, Jan 6, 2025 at 11:44 AM Jerome Brunet <jbrunet@xxxxxxxxxxxx> wrote:
[...]
> > I have further verified that the gx-card parsing does find the HDMi
> > controller and links it correctly.
> > To me it's odd that only the .prepare() callback is not called, all
> > others (as mentioned above: .hw_params, .startup, ...) are working
> > fine.
>
> I think the problem you are seeing comes from the quirk of
> codec-to-codec links. The hdmi codec link is such a link on Amlogic
> because further digital routing is required after the backend.
>
> Those type of links are not used much beside some
> CPU offloading on Samsung and Amlogic, as far as I know.
> It is possible, even likely, that things are still missing there.
>
> So those C2C links are operated by the DAPM events, not the regualar
> ASoC code. You can start here:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/sound/soc/soc-dapm.c#n3995
Thank you - that is indeed the root cause!

> You'll see that .prepare() is not called, same as .trigger()
> That should propably be fixed :/
Since I'm still very much clueless about all of this I just came up
with an experimental patch. Any feedback on it is welcome (I can send
it as RFC patch - but prepare for me needing support).
With the attached patch I now see hdmi-codec's .prepare callback being called:
$ speaker-test -c2

speaker-test 1.2.13

Playback device is default
Stream parameters are 48000Hz, S16_LE, 2 channels
Using 16 octaves of pink noise
Rate set to 48000Hz (requested 48000Hz)
Buffer size range from 128 to 262144
Period size range from 64 to 131072
Periods = 4
[   42.043413] hdmi-audio-codec hdmi-audio-codec.0.auto:
hdmi_codec_hw_params() width 16 rate 48000 channels 2
[   42.047916] hdmi-audio-codec hdmi-audio-codec.0.auto:
hdmi_codec_prepare() width 16 rate 48000 channels 2



Best regards,
Martin

diff --git a/include/sound/soc-dai.h b/include/sound/soc-dai.h
index aab57c19f62b..a11501752637 100644
--- a/include/sound/soc-dai.h
+++ b/include/sound/soc-dai.h
@@ -193,6 +193,9 @@ int snd_soc_dai_set_channel_map(struct snd_soc_dai *dai,
 
 int snd_soc_dai_set_tristate(struct snd_soc_dai *dai, int tristate);
 
+int snd_soc_dai_prepare(struct snd_soc_dai *dai,
+			struct snd_pcm_substream *substream);
+
 /* Digital Audio Interface mute */
 int snd_soc_dai_digital_mute(struct snd_soc_dai *dai, int mute,
 			     int direction);
diff --git a/sound/soc/soc-dai.c b/sound/soc/soc-dai.c
index 34ba1a93a4c9..8e81783e5be9 100644
--- a/sound/soc/soc-dai.c
+++ b/sound/soc/soc-dai.c
@@ -360,6 +360,18 @@ int snd_soc_dai_set_tristate(struct snd_soc_dai *dai, int tristate)
 }
 EXPORT_SYMBOL_GPL(snd_soc_dai_set_tristate);
 
+int snd_soc_dai_prepare(struct snd_soc_dai *dai,
+			struct snd_pcm_substream *substream)
+{
+	int ret = 0;
+
+	if (dai->driver->ops &&
+	    dai->driver->ops->prepare)
+		ret = dai->driver->ops->prepare(substream, dai);
+
+	return soc_dai_ret(dai, ret);
+}
+
 /**
  * snd_soc_dai_digital_mute - configure DAI system or master clock.
  * @dai: DAI
diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
index 99521c784a9b..ac8eef217dc4 100644
--- a/sound/soc/soc-dapm.c
+++ b/sound/soc/soc-dapm.c
@@ -4013,6 +4013,13 @@ static int snd_soc_dai_link_event(struct snd_soc_dapm_widget *w,
 		break;
 
 	case SND_SOC_DAPM_POST_PMU:
+		snd_soc_dapm_widget_for_each_sink_path(w, path) {
+			sink = path->sink->priv;
+
+			snd_soc_dai_prepare(sink, substream);
+			ret = 0;
+		}
+
 		snd_soc_dapm_widget_for_each_sink_path(w, path) {
 			sink = path->sink->priv;