ErosQ Native: Add DC Offset to PCM data

A small negative offset seems to silence all
play/pause clicking on the PCM5102A.

Also adding PCM soft muting, and muting the headphone amp
when the headphones are detected as removed. This has been
tested to not cause any unintended side effects on the
line out.

Also confirmed the numerical dB values are (approx.) correct.

Change-Id: I689d68887c86add9cc5e0ccb0c7de01aaa69b4d9

1 files changed, 4 insertions, 0 deletions

diff --git a/firmware/pcm_sw_volume.c b/firmware/pcm_sw_volume.c
index 7322269f44..3593c684af 100644
--- a/firmware/pcm_sw_volume.c
+++ b/firmware/pcm_sw_volume.c
@@ -54,7 +54,11 @@ static typeof (memcpy) *pcm_scaling_fn = NULL;
 /* Scale sample by PCM factor */
 static inline int32_t pcm_scale_sample(PCM_F_T f, int32_t s)
 {
+#if defined(PCM_DC_OFFSET_VALUE)
+    return (f * s + PCM_DC_OFFSET_VALUE) >> PCM_SW_VOLUME_FRACBITS;
+#else
     return (f * s) >> PCM_SW_VOLUME_FRACBITS;
+#endif
 }
 
 /* Both UNITY, use direct copy */