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[media] ts2020: improve filter limit calc 

* We don't need calculate channel bandwidth from symbol rate as it
is calculated by DVB core.

* Use clamp() to force upper/lower limit of filter 3dB frequency.
Upper limit should never exceeded 40MHz (80MHz BW) in any case,
though...

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
This commit is contained in:
Antti Palosaari 2015-03-26 10:49:17 -03:00 committed by Mauro Carvalho Chehab
parent af9d525553
commit 2ca58f45cc
1 changed files with 3 additions and 7 deletions
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10
drivers/media/dvb-frontends/ts2020.c
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@ -233,7 +233,6 @@ static int ts2020_set_params(struct dvb_frontend *fe)
struct dtv_frontend_properties *c = &fe->dtv_property_cache;
struct ts2020_priv *priv = fe->tuner_priv;
int ret;
u32 symbol_rate = (c->symbol_rate / 1000);
u32 f3db, gdiv28;
u16 u16tmp, value, lpf_coeff;
u8 buf[3], reg10, lpf_mxdiv, mlpf_max, mlpf_min, nlpf;
@ -312,12 +311,9 @@ static int ts2020_set_params(struct dvb_frontend *fe)
value = ts2020_readreg(fe, 0x26);
f3db = (symbol_rate * 135) / 200 + 2000;
f3db += FREQ_OFFSET_LOW_SYM_RATE;
if (f3db < 7000)
f3db = 7000;
if (f3db > 40000)
f3db = 40000;
f3db = (c->bandwidth_hz / 1000 / 2) + 2000;
f3db += FREQ_OFFSET_LOW_SYM_RATE; /* FIXME: ~always too wide filter */
f3db = clamp(f3db, 7000U, 40000U);
gdiv28 = gdiv28 * 207 / (value * 2 + 151);
mlpf_max = gdiv28 * 135 / 100;