From: Mauro Carvalho Chehab Date: Fri, 1 Jul 2016 14:03:16 +0000 (-0300) Subject: [media] cxd2841er: adjust the dB scale for DVB-C X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=d12b791e3db757c42484342a015f26990642fdcb;p=linux-beck.git [media] cxd2841er: adjust the dB scale for DVB-C Instead of using a relative frequency range, calibrate it to show the results in dB. The callibration was done getting samples with a signal generated from -50dBm to -12dBm, incremented in steps of 0.5 dB, using 3 frequencies: 175 MHz, 410 MHz and 800 MHz. The modulated signal was using QAM64, and it was used a linear interpolation of all the results. Signed-off-by: Mauro Carvalho Chehab --- diff --git a/drivers/media/dvb-frontends/cxd2841er.c b/drivers/media/dvb-frontends/cxd2841er.c index 2a698711d25b..95d82c4445e2 100644 --- a/drivers/media/dvb-frontends/cxd2841er.c +++ b/drivers/media/dvb-frontends/cxd2841er.c @@ -1768,8 +1768,13 @@ static void cxd2841er_read_signal_strength(struct dvb_frontend *fe) case SYS_DVBC_ANNEX_A: strength = cxd2841er_read_agc_gain_t_t2(priv, p->delivery_system); - p->strength.stat[0].scale = FE_SCALE_RELATIVE; - p->strength.stat[0].uvalue = strength; + p->strength.stat[0].scale = FE_SCALE_DECIBEL; + /* + * Formula was empirically determinated via linear regression, + * using frequencies: 175 MHz, 410 MHz and 800 MHz, and a + * stream modulated with QAM64 + */ + p->strength.stat[0].uvalue = ((s32)strength) * 4045 / 1000 - 85224; break; case SYS_ISDBT: strength = 65535 - cxd2841er_read_agc_gain_i(