The ASP1 DOUT line must be defaulted to be high-impedance when
it is not actually transmitting data for an active channel.
In non-SoundWire modes ASP1 will usually be shared by multiple
amps so each amp must only drive the line during the slot for
an enabled TX channel.
In SoundWire mode a custom firmware can use ASP1 as a secondary
chip-to-chip audio link or as GPIO. It should be defaulted to
high-impedance since by default the purpose of this pin is not
known.
Backport note:
On kernel versions before 6.6 the cs35l56->base.regmap argument
to regmap_set_bits() must be changed to cs35l56->regmap.
Signed-off-by: Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx>
Fixes: e49611252900 ("ASoC: cs35l56: Add driver for Cirrus Logic CS35L56")
---
sound/soc/codecs/cs35l56.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/sound/soc/codecs/cs35l56.c b/sound/soc/codecs/cs35l56.c
index 8ccdd3f134a5..45b4de3eff94 100644
--- a/sound/soc/codecs/cs35l56.c
+++ b/sound/soc/codecs/cs35l56.c
@@ -1197,6 +1197,12 @@ int cs35l56_init(struct cs35l56_private *cs35l56)
/* Registers could be dirty after soft reset or SoundWire enumeration */
regcache_sync(cs35l56->base.regmap);
+ /* Set ASP1 DOUT to high-impedance when it is not transmitting audio data. */
+ ret = regmap_set_bits(cs35l56->base.regmap, CS35L56_ASP1_CONTROL3,
+ CS35L56_ASP1_DOUT_HIZ_CTRL_MASK);
+ if (ret)
+ return dev_err_probe(cs35l56->base.dev, ret, "Failed to write ASP1_CONTROL3\n");
+
cs35l56->base.init_done = true;
complete(&cs35l56->init_completion);
--
2.30.2
