Re: [RFC PATCH v2 4/6] ASoC: soc-pcm: tweak DPCM BE hw_param() call order

Ranjani Sridharan
2022-03-28T15:29:49Z

On Mon, 2022-03-28 at 11:44 +0530, Sameer Pujar wrote:
> For DPCM links, the order of hw_param() call depends on the sequence
> of
> BE connection to FE. It is possible that one BE link can provide
> clock
> to another BE link. In such cases consumer BE DAI, to get the rate
> set
> by provider BE DAI, can use the standard clock functions only if
> provider
> has already set the appropriate rate during its hw_param() stage.
>
> Presently the order is fixed and does not depend on the provider and
> consumer relationships. So the clock rates need to be known ahead of
> hw_param() stage.
>
> This patch tweaks the hw_param() order by connecting the provider BEs
> late to a FE. With this hw_param() calls for provider BEs happen
> first
> and then followed by consumer BEs. The consumers can use the standard
> clk_get_rate() function to get the rate of the clock they depend on.
>
> Signed-off-by: Sameer Pujar <spujar@nvidia.com>
> ---
> TODO:
> * The FE link is not considered in this. For Tegra it is fine to
> call hw_params() for FE at the end. But systems, which want to
> apply
> this tweak for FE as well, have to extend this tweak to FE.
> * Also only DPCM is considered here. If normal links require such
> tweak, it needs to be extended.
>
> sound/soc/soc-pcm.c | 60
> ++++++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 59 insertions(+), 1 deletion(-)
>
> diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
> index 9a95468..5829514 100644
> --- a/sound/soc/soc-pcm.c
> +++ b/sound/soc/soc-pcm.c
> @@ -1442,6 +1442,29 @@ static int dpcm_prune_paths(struct
> snd_soc_pcm_runtime *fe, int stream,
> return prune;
> }
>
> +static bool defer_dpcm_be_connect(struct snd_soc_pcm_runtime *rtd)
> +{
> + struct snd_soc_dai *dai;
> + int i;
> +
> + if (!(rtd->dai_link->dai_fmt & SND_SOC_DAIFMT_FORMAT_MASK))
> + return false;
Is this check necessary?
> +
> + if ((rtd->dai_link->dai_fmt &
> SND_SOC_DAIFMT_CLOCK_PROVIDER_MASK) ==
> + SND_SOC_DAIFMT_CBC_CFC) {
> +
> + for_each_rtd_cpu_dais(rtd, i, dai) {
> +
> + if (!snd_soc_dai_is_dummy(dai))
> + return true;
> + }
> + }
> +
> + return false;
> +}
> +
> +#define MAX_CLK_PROVIDER_BE 10
> +
> static int dpcm_add_paths(struct snd_soc_pcm_runtime *fe, int
> stream,
> struct snd_soc_dapm_widget_list **list_)
> {
> @@ -1449,7 +1472,8 @@ static int dpcm_add_paths(struct
> snd_soc_pcm_runtime *fe, int stream,
> struct snd_soc_dapm_widget_list *list = *list_;
> struct snd_soc_pcm_runtime *be;
> struct snd_soc_dapm_widget *widget;
> - int i, new = 0, err;
> + struct snd_soc_pcm_runtime *prov[MAX_CLK_PROVIDER_BE];
> + int i, new = 0, err, count = 0;
>
> /* Create any new FE <--> BE connections */
> for_each_dapm_widgets(list, i, widget) {
> @@ -1489,6 +1513,40 @@ static int dpcm_add_paths(struct
> snd_soc_pcm_runtime *fe, int stream,
> (be->dpcm[stream].state !=
> SND_SOC_DPCM_STATE_CLOSE))
> continue;
>
> + /* Connect clock provider BEs at the end */
> + if (defer_dpcm_be_connect(be)) {
> + if (count >= MAX_CLK_PROVIDER_BE) {
What determines MAX_CLK_PROVIDER_BE? why 10? Can you use rtd->num_cpus
instead?
Thanks,
Ranjani