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

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Message-ID: <20200304102406.8093-1-olivier.moysan@st.com>
Date:   Wed, 4 Mar 2020 11:24:06 +0100
From:   Olivier Moysan <olivier.moysan@...com>
To:     <lgirdwood@...il.com>, <broonie@...nel.org>, <perex@...ex.cz>,
        <tiwai@...e.com>, <alexandre.torgue@...com>,
        <olivier.moysan@...com>
CC:     <alsa-devel@...a-project.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-kernel@...r.kernel.org>, <srinivas.kandagatla@...aro.org>
Subject: [PATCH] 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 may be no more functional. The following problems have been seen
with STM32 SAI driver.

1) DMA channel is not requested:

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

2) DMA channel is not released:

dma_release_channel() is not called when
devm_dmaengine_pcm_release() is executed.
This occurs because SND_DMAENGINE_PCM_DRV_NAME component,
has already been released through devm_component_release().

devm_dmaengine_pcm_release() should be called before
devm_component_release() to avoid this problem.

Call snd_dmaengine_pcm_unregister() and snd_soc_unregister_component()
explicitly from SAI driver, to have the right sequence.

Signed-off-by: Olivier Moysan <olivier.moysan@...com>
---
 sound/soc/stm/stm32_sai_sub.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/sound/soc/stm/stm32_sai_sub.c b/sound/soc/stm/stm32_sai_sub.c
index 0bbf9ed5e48b..48dfcdd13574 100644
--- a/sound/soc/stm/stm32_sai_sub.c
+++ b/sound/soc/stm/stm32_sai_sub.c
@@ -1547,21 +1547,21 @@ static int stm32_sai_sub_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	ret = devm_snd_soc_register_component(&pdev->dev, &stm32_component,
-					      &sai->cpu_dai_drv, 1);
-	if (ret)
-		return ret;
-
-	if (STM_SAI_PROTOCOL_IS_SPDIF(sai))
-		conf = &stm32_sai_pcm_config_spdif;
-
-	ret = devm_snd_dmaengine_pcm_register(&pdev->dev, conf, 0);
+	ret = snd_dmaengine_pcm_register(&pdev->dev, conf, 0);
 	if (ret) {
 		if (ret != -EPROBE_DEFER)
 			dev_err(&pdev->dev, "PCM DMA register error %d\n", ret);
 		return ret;
 	}
 
+	ret = snd_soc_register_component(&pdev->dev, &stm32_component,
+					 &sai->cpu_dai_drv, 1);
+	if (ret)
+		return ret;
+
+	if (STM_SAI_PROTOCOL_IS_SPDIF(sai))
+		conf = &stm32_sai_pcm_config_spdif;
+
 	return 0;
 }
 
@@ -1570,6 +1570,8 @@ static int stm32_sai_sub_remove(struct platform_device *pdev)
 	struct stm32_sai_sub_data *sai = dev_get_drvdata(&pdev->dev);
 
 	clk_unprepare(sai->pdata->pclk);
+	snd_dmaengine_pcm_unregister(&pdev->dev);
+	snd_soc_unregister_component(&pdev->dev);
 
 	return 0;
 }
-- 
2.17.1