ASoC: soc-component: add snd_soc_pcm_component_delay()

Current soc-pcm.c :: soc_pcm_pointer() is assuming that
component driver might update runtime->delay silently in
snd_soc_pcm_component_pointer() (= A).

	static snd_pcm_uframes_t soc_pcm_pointer(...)
	{
		...

		/* clearing the previous total delay */
=>		runtime->delay = 0;

(A)		offset = snd_soc_pcm_component_pointer(substream);

		/* base delay if assigned in pointer callback */
=>		delay = runtime->delay;
		...
	}

1) The behavior that ".pointer callback secretly updates
   runtime->delay" is strange and confusable.

2) Current snd_soc_pcm_component_pointer() uses 1st found component's
   .pointer callback only, thus it is no problem for now.
   But runtime->delay might be overwrote if it adjusted to multiple
   components in the future.

3) Component delay is updated at .pointer callback timing (secretly).
   But some components which doesn't have .pointer callback might want
   to increase runtime->delay for some reasons.

We already have .delay function for DAI, but not have for Component.
This patch adds new snd_soc_pcm_component_delay() for it.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/874k8cy25t.wl-kuninori.morimoto.gx@renesas.comSigned-off-by: Mark Brown <broonie@kernel.org>

include/sound/soc-component.h

@@ -148,6 +148,8 @@ struct snd_soc_component_driver {
 		    struct vm_area_struct *vma);
 	int (*ack)(struct snd_soc_component *component,
 		   struct snd_pcm_substream *substream);
+	snd_pcm_sframes_t (*delay)(struct snd_soc_component *component,
+				   struct snd_pcm_substream *substream);
 
 	const struct snd_compress_ops *compress_ops;
 
@@ -505,5 +507,7 @@ int snd_soc_pcm_component_pm_runtime_get(struct snd_soc_pcm_runtime *rtd,
 void snd_soc_pcm_component_pm_runtime_put(struct snd_soc_pcm_runtime *rtd,
 					  void *stream, int rollback);
 int snd_soc_pcm_component_ack(struct snd_pcm_substream *substream);
+void snd_soc_pcm_component_delay(struct snd_pcm_substream *substream,
+				 snd_pcm_sframes_t *cpu_delay, snd_pcm_sframes_t *codec_delay);
 
 #endif /* __SOC_COMPONENT_H */

sound/soc/soc-component.c

@@ -932,6 +932,34 @@ int snd_soc_pcm_component_pointer(struct snd_pcm_substream *substream)
 	return 0;
 }
 
+void snd_soc_pcm_component_delay(struct snd_pcm_substream *substream,
+				 snd_pcm_sframes_t *cpu_delay,
+				 snd_pcm_sframes_t *codec_delay)
+{
+	struct snd_soc_pcm_runtime *rtd = asoc_substream_to_rtd(substream);
+	struct snd_soc_component *component;
+	snd_pcm_sframes_t delay;
+	int i;
+
+	/*
+	 * We're looking for the delay through the full audio path so it needs to
+	 * be the maximum of the Components doing transmit and the maximum of the
+	 * Components doing receive (ie, all CPUs and all CODECs) rather than
+	 * just the maximum of all Components.
+	 */
+	for_each_rtd_components(rtd, i, component) {
+		if (!component->driver->delay)
+			continue;
+
+		delay = component->driver->delay(component, substream);
+
+		if (snd_soc_component_is_codec(component))
+			*codec_delay = max(*codec_delay, delay);
+		else
+			*cpu_delay = max(*cpu_delay, delay);
+	}
+}
+
 int snd_soc_pcm_component_ioctl(struct snd_pcm_substream *substream,
 				unsigned int cmd, void *arg)
 {

sound/soc/soc-pcm.c

@@ -1098,7 +1098,9 @@ static snd_pcm_uframes_t soc_pcm_pointer(struct snd_pcm_substream *substream)
 	/* base delay if assigned in pointer callback */
 	delay = runtime->delay;
 
+	/* should be called *after* snd_soc_pcm_component_pointer() */
 	snd_soc_pcm_dai_delay(substream, &cpu_delay, &codec_delay);
+	snd_soc_pcm_component_delay(substream, &cpu_delay, &codec_delay);
 
 	runtime->delay = delay + cpu_delay + codec_delay;