V4L/DVB (6656): zl10353: store frequencies in 0.1kHz to eliminate rou…

…nding 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>
git-mirror · Jan 25, 2008 · a1dcd9d · a1dcd9d
1 parent 702a676
commit a1dcd9d
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Showing 3 changed files with 14 additions and 11 deletions.
diff --git 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
@@ -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
@@ -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 */