V4L/DVB (6656): zl10353: store frequencies in 0.1kHz to eliminate rounding errors

Whilst reanalysing my formulas I realised it was no longer possible to get the
right values for a 36.1667MHz IF due to rounding problems.

Storing frequencies in units of 0.1kHz makes it possible to calculate these
again correctly.

Signed-off-by: Chris Pascoe <c.pascoe@itee.uq.edu.au>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

diff --git a/drivers/media/dvb/dvb-usb/cxusb.c b/drivers/media/dvb/dvb-usb/cxusb.c
index c44b9799efaa34dca76f222c665718e9e567a750..deeb3871a2aaf00c08baf06c0b3ad383c5840b9d 100644 (file)
--- a/drivers/media/dvb/dvb-usb/cxusb.c
+++ b/drivers/media/dvb/dvb-usb/cxusb.c
@@ -435,7 +435,7 @@ static struct mt352_config cxusb_mt352_config = {
 
 static struct zl10353_config cxusb_zl10353_xc3028_config = {
        .demod_address = 0x0f,
-       .if2 = 4560,
+       .if2 = 45600,
        .no_tuner = 1,
        .parallel_ts = 1,
 };

diff --git a/drivers/media/dvb/frontends/zl10353.c b/drivers/media/dvb/frontends/zl10353.c
index 1736c6ac39cccf6be33ee184f1a484b846620d0b..091fbcced0065918863f2cfbe01a7bc3b9b2c5d6 100644 (file)
--- a/drivers/media/dvb/frontends/zl10353.c
+++ b/drivers/media/dvb/frontends/zl10353.c
@@ -123,9 +123,10 @@ static void zl10353_calc_nominal_rate(struct dvb_frontend *fe,
                                      enum fe_bandwidth bandwidth,
                                      u16 *nominal_rate)
 {
-       u32 adc_clock = 45056; /* 45.056 MHz */
-       u8 bw;
        struct zl10353_state *state = fe->demodulator_priv;
+       u32 adc_clock = 450560; /* 45.056 MHz */
+       u64 value;
+       u8 bw;
 
        if (state->config.adc_clock)
                adc_clock = state->config.adc_clock;
@@ -143,7 +144,9 @@ static void zl10353_calc_nominal_rate(struct dvb_frontend *fe,
                break;
        }
 
-       *nominal_rate = (bw * (1 << 23) / 7 * 125 + adc_clock / 2) / adc_clock;
+       value = (bw * (u64)10 * (1 << 23) / 7 * 125 + adc_clock / 2);
+       do_div(value, adc_clock);
+       *nominal_rate = value;
 
        dprintk("%s: bw %d, adc_clock %d => 0x%x\n",
                __FUNCTION__, bw, adc_clock, *nominal_rate);
@@ -153,8 +156,8 @@ static void zl10353_calc_input_freq(struct dvb_frontend *fe,
                                    u16 *input_freq)
 {
        struct zl10353_state *state = fe->demodulator_priv;
-       u32 adc_clock = 45056;  /* 45.056 MHz */
-       int if2 = 36167;        /* 36.167 MHz */
+       u32 adc_clock = 450560; /* 45.056  MHz */
+       int if2 = 361667;       /* 36.1667 MHz */
        int ife;
        u64 value;
 
@@ -170,7 +173,7 @@ static void zl10353_calc_input_freq(struct dvb_frontend *fe,
                if (ife > adc_clock / 2)
                        ife = adc_clock - ife;
        }
-       value = 65536ULL * ife + adc_clock / 2;
+       value = (u64)65536 * ife + adc_clock / 2;
        do_div(value, adc_clock);
        *input_freq = -value;
 

diff --git a/drivers/media/dvb/frontends/zl10353.h b/drivers/media/dvb/frontends/zl10353.h
index 2660cec93f83700d10573613d4cc7a2ce123c1c4..fc734c22b5fa9d8231aa723698eb43746ba1d290 100644 (file)
--- a/drivers/media/dvb/frontends/zl10353.h
+++ b/drivers/media/dvb/frontends/zl10353.h
@@ -29,9 +29,9 @@ struct zl10353_config
        /* demodulator's I2C address */
        u8 demod_address;
 
-       /* frequencies in kHz */
-       int adc_clock;  /* default: 45056 */
-       int if2;        /* default: 36167 */
+       /* frequencies in units of 0.1kHz */
+       int adc_clock;  /* default: 450560 (45.056  MHz) */
+       int if2;        /* default: 361667 (36.1667 MHz) */
 
        /* set if no pll is connected to the secondary i2c bus */
        int no_tuner;
@@ -50,6 +50,6 @@ static inline struct dvb_frontend* zl10353_attach(const struct zl10353_config *c
        printk(KERN_WARNING "%s: driver disabled by Kconfig\n", __FUNCTION__);
        return NULL;
 }
-#endif // CONFIG_DVB_ZL10353
+#endif /* CONFIG_DVB_ZL10353 */
 
 #endif /* ZL10353_H */