Re: [RFC PATCH v1 2/2] ASoC: dapm: add support for preparing streams

[Jerome Brunet <jbrunet@xxxxxxxxxxxx>]

On Mon 06 Jan 2025 at 15:13, Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx> wrote:

> Codec driver can implement .hw_params and/or .prepare from struct
> snd_soc_dai_ops. For codec-to-codec links only the former (.hw_params)
> callback has been called.
>
> On platforms like Amlogic Meson8/8b/8m2 the SoC's sound card
> (sound/soc/meson/gx-card.c) uses a codec-to-codec link for the HDMI
> codec output because further digital routing is required after the
> backend. The new DRM HDMI (audio) codec framework (which internally
> uses sound/soc/codecs/hdmi-codec.c) relies on the .prepare callback
> of the hdmi-codec to be called. Implement a call to
> snd_soc_dai_prepare() so the .prepare callback of the hdmi-codec is
> called on those platforms.
>
> For platforms or sound cards without a codec-to-codec link with
> additional parameters (which applies to most hardware) this changes
> nothing as the .prepare callback is already called via
> snd_pcm_do_prepare() (as well as dpcm_fe_dai_prepare() and
> dpcm_be_dai_prepare()) on those.
>
> Suggested-by: Jerome Brunet <jbrunet@xxxxxxxxxxxx>
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>

Thanks for working on this. Overall it looks good.

Not sure if the call the .prepare() should go at the beginning of
POST_PMU, as done here, or at the end of PRE_PMU ? 

> ---
>  sound/soc/soc-dapm.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> 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;

-- 
Jerome