[RFC] ASoC: dai playback_active and capture_active may be greater than 1

Message ID 20180419140612.11049-1-jbrunet@baylibre.com
State New
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  • [RFC] ASoC: dai playback_active and capture_active may be greater than 1
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Commit Message

Jerome Brunet April 19, 2018, 2:06 p.m.
At the moment playback_active and capture_active are using only 1 bit so
the maximum active count is 1.

However, snd_soc_runtime_activate() may be called several time on the
same dai. This happens when a dai is part of several dai_links. It is
often the case for "snd-soc-dummy-dai".

This is a problem if snd_soc_runtime_activate() is called an even number
of times on a dai. In this case the active count overflow back to 0. As
consequence, ASoC functions, such as soc_dpcm_runtime_update(), won't run
correctly.

Storing these usage counts on plain 'unsigned int' solves the problem.

Fixes: f0fba2ad1b6b ("ASoC: multi-component - ASoC Multi-Component Support")
Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>

---

Hi,

I found this problem while working on ASoC support for a new platform.
During a playback, using DPCM, if I changed the backend dai, nothing
happened, old backend path was not pruned, new backend path was not added.

Here is how it goes:
1 FE and 2 BE, all 3 using snd-soc-dummy-dai for the codec_dai (ATM).

On playback start:
 - BE #1 activates and increments snd-soc-dummy-dai's playback_active
 - FE activates and increments snd-soc-dummy-dai's playback_active

The playback works but snd-soc-dummy-dai's playback_active value is now 0.

Through a mux kcontrol, change BE client of FE, from BE #1 to BE #2.
 -> trigger soc_dpcm_runtime_update().
    -> checks fe's codec_dai playback_active which is zero so playback
    path processing is skipped, keeping the old invalid path.

 include/sound/soc-dai.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

-- 
2.14.3

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Comments

Charles Keepax April 30, 2018, 3:10 p.m. | #1
On Thu, Apr 19, 2018 at 04:06:12PM +0200, Jerome Brunet wrote:
> At the moment playback_active and capture_active are using only 1 bit so

> the maximum active count is 1.

> 

> However, snd_soc_runtime_activate() may be called several time on the

> same dai. This happens when a dai is part of several dai_links. It is

> often the case for "snd-soc-dummy-dai".

> 

> This is a problem if snd_soc_runtime_activate() is called an even number

> of times on a dai. In this case the active count overflow back to 0. As

> consequence, ASoC functions, such as soc_dpcm_runtime_update(), won't run

> correctly.

> 

> Storing these usage counts on plain 'unsigned int' solves the problem.

> 

> Fixes: f0fba2ad1b6b ("ASoC: multi-component - ASoC Multi-Component Support")

> Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>

> ---


Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>


Thanks,
Charles
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Patch

diff --git a/include/sound/soc-dai.h b/include/sound/soc-dai.h
index 8ad11669e4d8..35ebb0be5114 100644
--- a/include/sound/soc-dai.h
+++ b/include/sound/soc-dai.h
@@ -294,8 +294,8 @@  struct snd_soc_dai {
 	struct snd_soc_dai_driver *driver;
 
 	/* DAI runtime info */
-	unsigned int capture_active:1;		/* stream is in use */
-	unsigned int playback_active:1;		/* stream is in use */
+	unsigned int capture_active;		/* stream usage count */
+	unsigned int playback_active;		/* stream usage count */
 	unsigned int probed:1;
 
 	unsigned int active;