The volume control for cs42l43 speakers has a maximum gain of +31.5 dB.
However, for many use cases, this can cause distorted audio, depending
various factors, such as other signal-processing elements in the chain,
for example if the audio passes through a gain control before reaching
the codec or the signal path has been tuned for a particular maximum
gain in the codec.

In the case of systems which use the soc_sdw_cs42l43 driver, audio will
likely be distorted in all cases above 0 dB, therefore add a volume
limit of 128, which is 0 dB maximum volume inside this driver.

Signed-off-by: Stefan Binding <sbinding@opensource.cirrus.com>
---
 sound/soc/sdw_utils/soc_sdw_cs42l43.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/sound/soc/sdw_utils/soc_sdw_cs42l43.c b/sound/soc/sdw_utils/soc_sdw_cs42l43.c
index 668c9d28a1c1..b415d45d520d 100644
--- a/sound/soc/sdw_utils/soc_sdw_cs42l43.c
+++ b/sound/soc/sdw_utils/soc_sdw_cs42l43.c
@@ -20,6 +20,8 @@
 #include <sound/soc-dapm.h>
 #include <sound/soc_sdw_utils.h>
 
+#define CS42L43_SPK_VOLUME_0DB	128 /* 0dB Max */
+
 static const struct snd_soc_dapm_route cs42l43_hs_map[] = {
 	{ "Headphone", NULL, "cs42l43 AMP3_OUT" },
 	{ "Headphone", NULL, "cs42l43 AMP4_OUT" },
@@ -117,6 +119,14 @@ int asoc_sdw_cs42l43_spk_rtd_init(struct snd_soc_pcm_runtime *rtd, struct snd_so
 			return -ENOMEM;
 	}
 
+	ret = snd_soc_limit_volume(card, "cs42l43 Speaker Digital Volume",
+				   CS42L43_SPK_VOLUME_0DB);
+	if (ret)
+		dev_err(card->dev, "cs42l43 speaker volume limit failed: %d\n", ret);
+	else
+		dev_info(card->dev, "Setting CS42L43 Speaker volume limit to %d\n",
+			 CS42L43_SPK_VOLUME_0DB);
+
 	ret = snd_soc_dapm_add_routes(&card->dapm, cs42l43_spk_map,
 				      ARRAY_SIZE(cs42l43_spk_map));
 	if (ret)
-- 
2.43.0

On Wed, Apr 30, 2025 at 11:31:19AM +0100, Stefan Binding wrote:
> The volume control for cs42l43 speakers has a maximum gain of +31.5 dB.
> However, for many use cases, this can cause distorted audio, depending
> various factors, such as other signal-processing elements in the chain,
> for example if the audio passes through a gain control before reaching
> the codec or the signal path has been tuned for a particular maximum
> gain in the codec.
> 
> In the case of systems which use the soc_sdw_cs42l43 driver, audio will
> likely be distorted in all cases above 0 dB, therefore add a volume
> limit of 128, which is 0 dB maximum volume inside this driver.
> 
> Signed-off-by: Stefan Binding <sbinding@opensource.cirrus.com>
> ---

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

Thanks,
Charles