diff --git a/firmware/drivers/tuner/rda5802.c b/firmware/drivers/tuner/rda5802.c
index 3f122714bd..55e775e985 100644
--- a/firmware/drivers/tuner/rda5802.c
+++ b/firmware/drivers/tuner/rda5802.c
@@ -48,9 +48,9 @@
 #define SYSCONFIG1  0x4
 #define SYSCONFIG2  0x5
 #define SYSCONFIG3  0x6
-#define SYSCONFIG4  0x7 /* undocumented */
-#define SYSCONFIG5  0x8 /* undocumented */
-#define SYSCONFIG6  0x9 /* undocumented */
+#define SYSCONFIG4  0x7
+#define SYSCONFIG5  0x8
+#define SYSCONFIG6  0x9 /* suspected not to exists */
 #define READCHAN    0xA
 #define STATUSRSSI  0xB
 
@@ -81,7 +81,7 @@
 
 /* SYSCONFIG1 (0x4) */
 #define SYSCONFIG1_DE       (0x1 << 11)
-    #define SYSCONFIG1_SOFTMUTE_EN  (0x1 << 9)
+#define SYSCONFIG1_SOFTMUTE_EN  (0x1 << 9)
 
 /* SYSCONFIG2 (0x5) */
 #define SYSCONFIG2_VOLUME   (0xF <<  0)
@@ -105,9 +105,9 @@ static uint16_t cache[16] = {
     [SYSCONFIG1] =  0x0200, /* SYSCONFIG1_SOFTMUTE_EN */
     [SYSCONFIG2] =  0x867F, /* INT_MODE (def), SEEKTH=1100b, LNA_PORT_SEL=LNAN,
                                LNA_ICSEL=3.0mA, VOLUME=max */
-    [SYSCONFIG3] =  0x8000, /* I2S slave mode */
-    [SYSCONFIG4] =  0x4712, /* undocumented, affects stereo blend */
-    [SYSCONFIG5] =  0x5EC6, /* undocumented */
+    [SYSCONFIG3] =  0x8000, /* RSVD */
+    [SYSCONFIG4] =  0x4712, /* TH_SOFRBLEND=34dB, 65M_50M MODE=65~76MHz, RSVD, SEEK_TH_OLD=4, SOFTBLEND_EN */
+    [SYSCONFIG5] =  0x5EC6, /* FREQ_DIRECT=24262kHz (unused) */
     [SYSCONFIG6] =  0x0000  /* undocumented */
 };