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authorChris Pascoe <c.pascoe@itee.uq.edu.au>2007-11-20 14:17:54 +0300
committerMauro Carvalho Chehab <mchehab@infradead.org>2008-01-26 00:02:37 +0300
commita1dcd9de648c8cf21abaeca7f77885665eed4117 (patch)
treef35cdf7d007056445a0603a12fb20d3eed5ec7ba /drivers/media/dvb/frontends/zl10353.c
parent702a67624e4bc9c7056418b576af928940b7dbb9 (diff)
downloadlinux-a1dcd9de648c8cf21abaeca7f77885665eed4117.tar.xz
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>
Diffstat (limited to 'drivers/media/dvb/frontends/zl10353.c')
-rw-r--r--drivers/media/dvb/frontends/zl10353.c15
1 files changed, 9 insertions, 6 deletions
diff --git a/drivers/media/dvb/frontends/zl10353.c b/drivers/media/dvb/frontends/zl10353.c
index 1736c6ac39cc..091fbcced006 100644
--- 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;