diff options
Diffstat (limited to 'drivers/media/dvb/frontends/tda18271c2dd.c')
| -rw-r--r-- | drivers/media/dvb/frontends/tda18271c2dd.c | 32 |
1 files changed, 17 insertions, 15 deletions
diff --git a/drivers/media/dvb/frontends/tda18271c2dd.c b/drivers/media/dvb/frontends/tda18271c2dd.c index 1b1bf200c55c..de544f6a4d70 100644 --- a/drivers/media/dvb/frontends/tda18271c2dd.c +++ b/drivers/media/dvb/frontends/tda18271c2dd.c @@ -1123,20 +1123,6 @@ static int release(struct dvb_frontend *fe) return 0; } -/* - * As defined on EN 300 429 Annex A and on ITU-T J.83 annex A, the DVB-C - * roll-off factor is 0.15. - * According with the specs, the amount of the needed bandwith is given by: - * Bw = Symbol_rate * (1 + 0.15) - * As such, the maximum symbol rate supported by 6 MHz is - * max_symbol_rate = 6 MHz / 1.15 = 5217391 Bauds - *NOTE: For ITU-T J.83 Annex C, the roll-off factor is 0.13. So: - * max_symbol_rate = 6 MHz / 1.13 = 5309735 Baud - * That means that an adjustment is needed for Japan, - * but, as currently DRX-K is hardcoded to Annex A, let's stick - * with 0.15 roll-off factor. - */ -#define MAX_SYMBOL_RATE_6MHz 5217391 static int set_params(struct dvb_frontend *fe, struct dvb_frontend_parameters *params) @@ -1144,6 +1130,7 @@ static int set_params(struct dvb_frontend *fe, struct tda_state *state = fe->tuner_priv; int status = 0; int Standard; + u32 bw; state->m_Frequency = params->frequency; @@ -1161,8 +1148,23 @@ static int set_params(struct dvb_frontend *fe, break; } else if (fe->ops.info.type == FE_QAM) { - if (params->u.qam.symbol_rate <= MAX_SYMBOL_RATE_6MHz) + /* + * Using a higher bandwidth at the tuner filter may + * allow inter-carrier interference. + * So, determine the minimal channel spacing, in order + * to better adjust the tuner filter. + * According with ITU-T J.83, the bandwidth is given by: + * bw = Simbol Rate * (1 + roll_off), where the roll_off + * is equal to 0.15 for Annex A, and 0.13 for annex C + */ + if (fe->dtv_property_cache.rolloff == ROLLOFF_13) + bw = (params->u.qam.symbol_rate * 13) / 10; + else + bw = (params->u.qam.symbol_rate * 15) / 10; + if (bw <= 6000000) Standard = HF_DVBC_6MHZ; + else if (bw <= 7000000) + Standard = HF_DVBC_7MHZ; else Standard = HF_DVBC_8MHZ; } else |