wm8758: document and fix audiohw settings

It looks like a copy and paste error to me, those were completely wrong.

Change-Id: Id6ae025f4216ffccb1a8b8b790916d8b6c4694bd

2 files changed, 7 insertions, 3 deletions

diff --git a/firmware/drivers/audio/wm8758.c b/firmware/drivers/audio/wm8758.c
index 9ae78191bf..df90081354 100644
--- a/firmware/drivers/audio/wm8758.c
+++ b/firmware/drivers/audio/wm8758.c
@@ -305,6 +305,7 @@ void audiohw_disable_recording(void)
     wmcodec_write(PWRMGMT2, PWRMGMT2_ROUT1EN | PWRMGMT2_LOUT1EN);
 }
 
+/* volume in 0 .. 63, corresponds to -12dB .. +35.25dB in 0.75dB steps */
 void audiohw_set_recvol(int left, int right, int type)
 {
     switch (type)
diff --git a/firmware/export/wm8758.h b/firmware/export/wm8758.h
index db6dd083dd..d4194b90ee 100644
--- a/firmware/export/wm8758.h
+++ b/firmware/export/wm8758.h
@@ -32,9 +32,12 @@ AUDIOHW_SETTING(TREBLE,      "dB", 0,  1, -12,  12,   0)
 AUDIOHW_SETTING(BASS_CUTOFF,   "", 0,  1,   1,   4,   1)
 AUDIOHW_SETTING(TREBLE_CUTOFF, "", 0,  1,   1,   4,   1)
 #ifdef HAVE_RECORDING
-AUDIOHW_SETTING(LEFT_GAIN,   "dB", 1,  1,   0,  63,  16, ((val - 23) * 15) / 2 + 200)
-AUDIOHW_SETTING(RIGHT_GAIN,  "dB", 1,  1,   0,  63,  16, ((val - 23) * 15) / 2 + 200)
-AUDIOHW_SETTING(MIC_GAIN,    "dB", 1,  1,   0,  63,  16, ((val - 23) * 15) / 2 + 200)
+/* The input PGAs have a gain range from -12dB to +35.25dB in 0.75dB steps
+ * Values: 0, 1, ..., 63
+ *      => -12dB, -11.25dB, ..., 35.25dB */
+AUDIOHW_SETTING(LEFT_GAIN,   "dB", 1,  1,   0,  63,  16, ((val) * 15) / 2 - 120)
+AUDIOHW_SETTING(RIGHT_GAIN,  "dB", 1,  1,   0,  63,  16, ((val) * 15) / 2 - 120)
+AUDIOHW_SETTING(MIC_GAIN,    "dB", 1,  1,   0,  63,  16, ((val) * 15) / 2 - 120)
 #endif /* HAVE_RECORDING */
 
 void audiohw_enable_lineout(bool enable);