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>

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;