V4L/DVB (6034): cx88: Add parameter to control radio deemphasis time constant

[linux-2.6-omap-h63xx.git] / drivers / media / video / cx88 / cx88-tvaudio.c

diff --git a/drivers/media/video/cx88/cx88-tvaudio.c b/drivers/media/video/cx88/cx88-tvaudio.c
index 99e120483ecd5e59066ca4ab8e4bed6141596e46..9aee8c51ee27f8d81db86ab316df0a6ebe50cea6 100644 (file)
--- a/drivers/media/video/cx88/cx88-tvaudio.c
+++ b/drivers/media/video/cx88/cx88-tvaudio.c
@@ -62,6 +62,10 @@ static unsigned int always_analog = 0;
 module_param(always_analog,int,0644);
 MODULE_PARM_DESC(always_analog,"force analog audio out");
 
+static unsigned int radio_deemphasis = 0;
+module_param(radio_deemphasis,int,0644);
+MODULE_PARM_DESC(radio_deemphasis, "Radio deemphasis time constant, "
+                "0=None, 1=50us (elsewhere), 2=75us (USA)");
 
 #define dprintk(fmt, arg...)   if (audio_debug) \
        printk(KERN_DEBUG "%s/0: " fmt, core->name , ## arg)
@@ -678,6 +682,10 @@ static void set_audio_standard_FM(struct cx88_core *core,
        };
 
        /* It is enough to leave default values? */
+       /* No, it's not!  The deemphasis registers are reset to the 75us
+        * values by default.  Analyzing the spectrum of the decoded audio
+        * reveals that "no deemphasis" is the same as 75 us, while the 50 us
+        * setting results in less deemphasis.  */
        static const struct rlist fm_no_deemph[] = {
 
                {AUD_POLYPH80SCALEFAC, 0x0003},
@@ -688,6 +696,7 @@ static void set_audio_standard_FM(struct cx88_core *core,
        set_audio_start(core, SEL_FMRADIO);
 
        switch (deemph) {
+       default:
        case FM_NO_DEEMPH:
                set_audio_registers(core, fm_no_deemph);
                break;
@@ -757,7 +766,7 @@ void cx88_set_tvaudio(struct cx88_core *core)
                set_audio_standard_EIAJ(core);
                break;
        case WW_FM:
-               set_audio_standard_FM(core, FM_NO_DEEMPH);
+               set_audio_standard_FM(core, radio_deemphasis);
                break;
        case WW_NONE:
        default: