[PATCH] ASoC: dai playback and capture active may be greater than 1

From: Jerome Brunet
Date: Fri Apr 27 2018 - 07:32:10 EST

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

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@xxxxxxxxxxxx>


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 is not pruned, new backend path is 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.

* No change since initial RFC [0], just droppped the RFC prefix.

[0]: https://lkml.kernel.org/r/20180419140612.11049-1-jbrunet@xxxxxxxxxxxx

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

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;