linux-kernel - [PATCH][RFC] ASoC: stm32: sai: manage rebind issue

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Date:   Fri, 22 Nov 2019 17:14:23 +0100
From:   Olivier Moysan <olivier.moysan@...com>
To:     <lgirdwood@...il.com>, <broonie@...nel.org>, <perex@...ex.cz>,
        <tiwai@...e.com>, <mcoquelin.stm32@...il.com>,
        <alexandre.torgue@...com>, <alsa-devel@...a-project.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-kernel@...r.kernel.org>, <olivier.moysan@...com>,
        <arnaud.pouliquen@...com>
CC:     <benjamin.gaignard@...com>, <srinivas.kandagatla@...aro.org>
Subject: [PATCH][RFC] ASoC: stm32: sai: manage rebind issue

The commit e894efef9ac7 ("ASoC: core: add support to card rebind")
allows to rebind the sound card after a rebind of one of its component.
With this commit, the sound card is actually rebound,
but is no more functional.

With the sound card rebind the simplified call sequence is:
stm32_sai_sub_probe
	snd_soc_register_component
		snd_soc_try_rebind_card
			snd_soc_instantiate_card
	devm_snd_dmaengine_pcm_register

The problem occurs because the pcm must be registered,
before snd_soc_instantiate_card() is called.

Modify SAI driver, to change the call sequence as follows:
stm32_sai_sub_probe
	devm_snd_dmaengine_pcm_register
	snd_soc_register_component
		snd_soc_try_rebind_card

---
The current patch allows to fix the issue for STM SAI driver.
However, most of the drivers register the component first.
So, this solution is perhaps not the right way to manage the problem.
This may probably be handled in ASoC framework instead.
---

Signed-off-by: Olivier Moysan <olivier.moysan@...com>
---
 sound/soc/stm/stm32_sai_sub.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/sound/soc/stm/stm32_sai_sub.c b/sound/soc/stm/stm32_sai_sub.c
index 48e629ac2d88..eb35306a1232 100644
--- a/sound/soc/stm/stm32_sai_sub.c
+++ b/sound/soc/stm/stm32_sai_sub.c
@@ -1484,6 +1484,13 @@ static int stm32_sai_sub_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	ret = devm_snd_dmaengine_pcm_register(&pdev->dev, conf, 0);
+	if (ret) {
+		dev_err(&pdev->dev, "Could not register pcm dma\n");
+		return ret;
+	}
+
+
 	ret = devm_snd_soc_register_component(&pdev->dev, &stm32_component,
 					      &sai->cpu_dai_drv, 1);
 	if (ret)
@@ -1492,11 +1499,6 @@ static int stm32_sai_sub_probe(struct platform_device *pdev)
 	if (STM_SAI_PROTOCOL_IS_SPDIF(sai))
 		conf = &stm32_sai_pcm_config_spdif;
 
-	ret = devm_snd_dmaengine_pcm_register(&pdev->dev, conf, 0);
-	if (ret) {
-		dev_err(&pdev->dev, "Could not register pcm dma\n");
-		return ret;
-	}
 
 	return 0;
 }
-- 
2.17.1