[PATCH v3 3/7] ASoC: meson: aiu-encoder-i2s: ensure clk divider gets disabled in hw_free

[Valerio Setti]

A recent Sashiko review [1] on this code revealed the following problem:

  If a user opens both streams so snd_soc_dai_active(dai) evaluates to 2,
  and explicitly calls SNDRV_PCM_IOCTL_HW_FREE before closing them,
  snd_soc_dai_active(dai) remains 2. This skips disabling the clock
  divider.
  When the streams are subsequently closed, the ALSA core skips invoking
  hw_free again because the state was already changed to
  SNDRV_PCM_STATE_OPEN. This would leave the clock divider permanently
  enabled, potentially draining battery or blocking system suspend.

This commit resolves this problem by using the 'clk_enabled' field of
'struct gx_stream'. In particular when 'hw_free()' is called on a stream
the code check what is the status of the other stream and then only if
both are off the clock divider is disabled.

[1]: https://lore.kernel.org/all/20260917212019.4ECE61F00893@smtp.kernel.org/

Signed-off-by: Valerio Setti <vsetti at baylibre.com>
---
 sound/soc/meson/aiu-encoder-i2s.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/sound/soc/meson/aiu-encoder-i2s.c b/sound/soc/meson/aiu-encoder-i2s.c
index 58dce9f08c9d..70ea39c77b32 100644
--- a/sound/soc/meson/aiu-encoder-i2s.c
+++ b/sound/soc/meson/aiu-encoder-i2s.c
@@ -219,16 +219,14 @@ static int aiu_encoder_i2s_hw_free(struct snd_pcm_substream *substream,
 				   struct snd_soc_dai *dai)
 {
 	struct gx_stream *ts = snd_soc_dai_get_dma_data(dai, substream);
+	struct gx_stream *other = snd_soc_dai_dma_data_get(dai, !substream->stream);
 	struct snd_soc_component *component = dai->component;
 
-	/*
-	 * If this is the last substream being closed then disable the i2s
-	 * clock divider.
-	 */
-	if (snd_soc_dai_active(dai) <= 1)
-		aiu_encoder_i2s_divider_enable(component, 0);
-
 	if (ts->clk_enabled) {
+		/* Disable the clk divider only if also the other stream is not using it */
+		if (!other || !other->clk_enabled)
+			aiu_encoder_i2s_divider_enable(component, false);
+
 		clk_disable_unprepare(ts->iface->mclk);
 		ts->clk_enabled = false;
 	}

-- 
2.47.3