[PATCH AUTOSEL 5.4 10/28] ASoC: soc-dapm: set bias_level if snd_soc_dapm_set_bias_level() was successed

[PATCH AUTOSEL 5.4 10/28] ASoC: soc-dapm: set bias_level if snd_soc_dapm_set_bias_level() was successed

[Sasha Levin]

From: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>

[ Upstream commit f40ecc2743652c0b0f19935f81baf57c601eb7f0 ]

ASoC has 2 functions to set bias level.
	(A) snd_soc_dapm_force_bias_level()
	(B) snd_soc_dapm_set_bias_level()

snd_soc_dapm_force_bias_level() (A) will set dapm->bias_level (a) if
successed.

(A)	int snd_soc_dapm_force_bias_level(...)
	{
		...
		if (ret == 0)
(a)			dapm->bias_level = level;
		...
	}

snd_soc_dapm_set_bias_level() (B) is also a function that sets bias_level.
It will call snd_soc_dapm_force_bias_level() (A) inside, but doesn't
set dapm->bias_level by itself. One note is that (A) might not be called.

(B)	static int snd_soc_dapm_set_bias_level(...)
	{
		...
		ret = snd_soc_card_set_bias_level(...);
		...
		if (dapm != &card->dapm)
(A)			ret = snd_soc_dapm_force_bias_level(...);
		...
		ret = snd_soc_card_set_bias_level_post(...);
		...
	}

dapm->bias_level will be set if (A) was called, but might not be set
if (B) was called, even though it calles set_bias_level() function.

We should set dapm->bias_level if we calls
snd_soc_dapm_set_bias_level() (B), too.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://patch.msgid.link/87qzyn4g4h.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

LLM Generated explanations, may be completely bogus:

Based on my analysis, here's my assessment:

**Backport Status: YES**

This commit should be backported to stable kernel trees for the
following reasons:

1. **Bug Fix**: This is a clear bug fix that addresses an inconsistency
   in bias level management. The commit message clearly explains that
   `snd_soc_dapm_set_bias_level()` doesn't always update
   `dapm->bias_level`, particularly when dealing with card-level DAPM
   contexts where `snd_soc_dapm_force_bias_level()` is not called.

2. **Small and Contained**: The fix is minimal - it only adds 4 lines of
   code:
  ```c
  /* success */
  if (ret == 0)
  snd_soc_dapm_init_bias_level(dapm, level);
  ```
  This ensures that `dapm->bias_level` is always updated when the bias
  level change succeeds.

3. **Important Correctness Issue**: The inconsistency could lead to
   incorrect bias level tracking, which affects power management
   decisions in the ASoC subsystem. Code that checks `dapm->bias_level`
   (as shown in lines like `if (dapm->bias_level == SND_SOC_BIAS_ON)`)
   may make wrong decisions if the bias level isn't properly tracked.

4. **No Architectural Changes**: This is a straightforward fix that
   doesn't introduce new features or change the architecture. It simply
   ensures consistent behavior between the two bias level setting
   functions.

5. **Low Risk**: The change only affects the success path (when `ret ==
   0`) and uses an existing inline function
   `snd_soc_dapm_init_bias_level()` that simply sets `dapm->bias_level =
   level`. This is the same operation that
   `snd_soc_dapm_force_bias_level()` performs on success.

6. **Affects User-Facing Functionality**: Incorrect bias level tracking
   can lead to power management issues, potentially causing audio
   devices to not power up/down correctly, which directly impacts users.

The commit fixes a real bug where the DAPM bias level state could become
out of sync with the actual hardware state, particularly for card-level
DAPM contexts. This is exactly the type of bug fix that stable kernels
should include - it's small, targeted, fixes a real issue, and has
minimal risk of introducing regressions.

 sound/soc/soc-dapm.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
index 9f764d92469e..6142ce468c3b 100644
--- a/sound/soc/soc-dapm.c
+++ b/sound/soc/soc-dapm.c
@@ -741,6 +741,10 @@ static int snd_soc_dapm_set_bias_level(struct snd_soc_dapm_context *dapm,
 out:
 	trace_snd_soc_bias_level_done(card, level);
 
+	/* success */
+	if (ret == 0)
+		snd_soc_dapm_init_bias_level(dapm, level);
+
 	return ret;
 }
 
-- 
2.39.5