[alsa-devel] [PATCH v2] ASoC: core: add support to card rebind

[Srinivas Kandagatla]

Current behaviour of ASoC core w.r.t to component removal is that it
unregisters dependent sound card totally. There is no support to
rebind the card if the component comes back.
Typical use case is DSP restart or kernel modules itself.

With this patch, core now maintains list of cards that are unbind due to
any of its depended components are removed and card not unregistered yet.
This list is cleared when the card is rebind successfully or when the
card is unregistered from machine driver.

This list of unbind cards are tried to bind once again after every new
component is successfully added, giving a fair chance for card bind
to be successful.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla at linaro.org>
---
Changes since v1:
	- None, just rebased on top of 
https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git/?h=for-next

 include/sound/soc.h  |  2 ++
 sound/soc/soc-core.c | 85 ++++++++++++++++++++++++++++++--------------
 2 files changed, 60 insertions(+), 27 deletions(-)

diff --git a/include/sound/soc.h b/include/sound/soc.h
index 821bf99992b8..46521b416aa1 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -1098,6 +1098,7 @@ struct snd_soc_card {
 
 	/* lists of probed devices belonging to this card */
 	struct list_head component_dev_list;
+	struct list_head list;
 
 	struct list_head widgets;
 	struct list_head paths;
@@ -1374,6 +1375,7 @@ static inline void snd_soc_initialize_card_lists(struct snd_soc_card *card)
 	INIT_LIST_HEAD(&card->dapm_list);
 	INIT_LIST_HEAD(&card->aux_comp_list);
 	INIT_LIST_HEAD(&card->component_dev_list);
+	INIT_LIST_HEAD(&card->list);
 }
 
 static inline bool snd_soc_volsw_is_stereo(struct soc_mixer_control *mc)
diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index 4e9367aacc0c..bc99bd5b2065 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -52,6 +52,7 @@ EXPORT_SYMBOL_GPL(snd_soc_debugfs_root);
 
 static DEFINE_MUTEX(client_mutex);
 static LIST_HEAD(component_list);
+static LIST_HEAD(unbind_card_list);
 
 /*
  * This is a timeout to do a DAPM powerdown after a stream is closed().
@@ -2681,6 +2682,33 @@ int snd_soc_dai_digital_mute(struct snd_soc_dai *dai, int mute,
 }
 EXPORT_SYMBOL_GPL(snd_soc_dai_digital_mute);
 
+static int snd_soc_bind_card(struct snd_soc_card *card)
+{
+	struct snd_soc_pcm_runtime *rtd;
+	int ret;
+
+	ret = snd_soc_instantiate_card(card);
+	if (ret != 0)
+		return ret;
+
+	/* deactivate pins to sleep state */
+	list_for_each_entry(rtd, &card->rtd_list, list)  {
+		struct snd_soc_dai *cpu_dai = rtd->cpu_dai;
+		struct snd_soc_dai *codec_dai;
+		int j;
+
+		for_each_rtd_codec_dai(rtd, j, codec_dai) {
+			if (!codec_dai->active)
+				pinctrl_pm_select_sleep_state(codec_dai->dev);
+		}
+
+		if (!cpu_dai->active)
+			pinctrl_pm_select_sleep_state(cpu_dai->dev);
+	}
+
+	return ret;
+}
+
 /**
  * snd_soc_register_card - Register a card with the ASoC core
  *
@@ -2690,7 +2718,6 @@ EXPORT_SYMBOL_GPL(snd_soc_dai_digital_mute);
 int snd_soc_register_card(struct snd_soc_card *card)
 {
 	int i, ret;
-	struct snd_soc_pcm_runtime *rtd;
 
 	if (!card->name || !card->dev)
 		return -EINVAL;
@@ -2722,28 +2749,23 @@ int snd_soc_register_card(struct snd_soc_card *card)
 	mutex_init(&card->mutex);
 	mutex_init(&card->dapm_mutex);
 
-	ret = snd_soc_instantiate_card(card);
-	if (ret != 0)
-		return ret;
-
-	/* deactivate pins to sleep state */
-	list_for_each_entry(rtd, &card->rtd_list, list)  {
-		struct snd_soc_dai *cpu_dai = rtd->cpu_dai;
-		struct snd_soc_dai *codec_dai;
-		int j;
-
-		for_each_rtd_codec_dai(rtd, j, codec_dai) {
-			if (!codec_dai->active)
-				pinctrl_pm_select_sleep_state(codec_dai->dev);
-		}
+	return snd_soc_bind_card(card);
+}
+EXPORT_SYMBOL_GPL(snd_soc_register_card);
 
-		if (!cpu_dai->active)
-			pinctrl_pm_select_sleep_state(cpu_dai->dev);
+static void snd_soc_unbind_card(struct snd_soc_card *card, bool unregister)
+{
+	if (card->instantiated) {
+		card->instantiated = false;
+		snd_soc_dapm_shutdown(card);
+		soc_cleanup_card_resources(card);
+		if (!unregister)
+			list_add(&card->list, &unbind_card_list);
+	} else {
+		if (unregister)
+			list_del(&card->list);
 	}
-
-	return ret;
 }
-EXPORT_SYMBOL_GPL(snd_soc_register_card);
 
 /**
  * snd_soc_unregister_card - Unregister a card with the ASoC core
@@ -2753,12 +2775,8 @@ EXPORT_SYMBOL_GPL(snd_soc_register_card);
  */
 int snd_soc_unregister_card(struct snd_soc_card *card)
 {
-	if (card->instantiated) {
-		card->instantiated = false;
-		snd_soc_dapm_shutdown(card);
-		soc_cleanup_card_resources(card);
-		dev_dbg(card->dev, "ASoC: Unregistered card '%s'\n", card->name);
-	}
+	snd_soc_unbind_card(card, true);
+	dev_dbg(card->dev, "ASoC: Unregistered card '%s'\n", card->name);
 
 	return 0;
 }
@@ -3102,7 +3120,7 @@ static void snd_soc_component_del_unlocked(struct snd_soc_component *component)
 	struct snd_soc_card *card = component->card;
 
 	if (card)
-		snd_soc_unregister_card(card);
+		snd_soc_unbind_card(card, false);
 
 	list_del(&component->list);
 }
@@ -3142,6 +3160,18 @@ static void convert_endianness_formats(struct snd_soc_pcm_stream *stream)
 			stream->formats |= endianness_format_map[i];
 }
 
+static void snd_soc_try_rebind_card(void)
+{
+	struct snd_soc_card *card, *c;
+
+	if (!list_empty(&unbind_card_list)) {
+		list_for_each_entry_safe(card, c, &unbind_card_list, list) {
+			if (!snd_soc_bind_card(card))
+				list_del(&card->list);
+		}
+	}
+}
+
 int snd_soc_add_component(struct device *dev,
 			struct snd_soc_component *component,
 			const struct snd_soc_component_driver *component_driver,
@@ -3169,6 +3199,7 @@ int snd_soc_add_component(struct device *dev,
 	}
 
 	snd_soc_component_add(component);
+	snd_soc_try_rebind_card();
 
 	return 0;
 
-- 
2.18.0