diff options
| author | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2016-07-01 15:41:38 -0300 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2016-07-16 06:56:28 -0300 |
| commit | 313a7dfb239f9433e5892d5a640f97b165b3e452 (patch) | |
| tree | e87613bf0bdaaecb2654a266d331a7b3bb8140f8 /drivers/media | |
| parent | d12b791e3db757c42484342a015f26990642fdcb (diff) | |
[media] cxd2841er: fix signal strength scale for ISDB-T
The scale for ISDB-T was wrong too: it was inverted, and
on a relative scale.
Use a linear interpolation to make it look better.
The formula was empirically determined, using 3 frequencies
(175 MHz, 410 MHz and 800 MHz), measuring from -50dBm to
-12dBm in steps of 0.5dB.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Diffstat (limited to 'drivers/media')
| -rw-r--r-- | drivers/media/dvb-frontends/cxd2841er.c | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/drivers/media/dvb-frontends/cxd2841er.c b/drivers/media/dvb-frontends/cxd2841er.c index 95d82c4445e2..2476d356069c 100644 --- a/drivers/media/dvb-frontends/cxd2841er.c +++ b/drivers/media/dvb-frontends/cxd2841er.c @@ -1746,7 +1746,7 @@ static void cxd2841er_read_signal_strength(struct dvb_frontend *fe) { struct dtv_frontend_properties *p = &fe->dtv_property_cache; struct cxd2841er_priv *priv = fe->demodulator_priv; - u32 strength; + s32 strength; dev_dbg(&priv->i2c->dev, "%s()\n", __func__); switch (p->delivery_system) { @@ -1763,7 +1763,7 @@ static void cxd2841er_read_signal_strength(struct dvb_frontend *fe) p->delivery_system); p->strength.stat[0].scale = FE_SCALE_DECIBEL; /* Formula was empirically determinated @ 410 MHz */ - p->strength.stat[0].uvalue = ((s32)strength) * 366 / 100 - 89520; + p->strength.stat[0].uvalue = strength * 366 / 100 - 89520; break; /* Code moved out of the function */ case SYS_DVBC_ANNEX_A: strength = cxd2841er_read_agc_gain_t_t2(priv, @@ -1774,13 +1774,16 @@ static void cxd2841er_read_signal_strength(struct dvb_frontend *fe) * 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; + p->strength.stat[0].uvalue = strength * 4045 / 1000 - 85224; break; case SYS_ISDBT: - strength = 65535 - cxd2841er_read_agc_gain_i( - priv, p->delivery_system); - p->strength.stat[0].scale = FE_SCALE_RELATIVE; - p->strength.stat[0].uvalue = strength; + strength = cxd2841er_read_agc_gain_i(priv, p->delivery_system); + p->strength.stat[0].scale = FE_SCALE_DECIBEL; + /* + * Formula was empirically determinated via linear regression, + * using frequencies: 175 MHz, 410 MHz and 800 MHz. + */ + p->strength.stat[0].uvalue = strength * 3775 / 1000 - 90185; break; case SYS_DVBS: case SYS_DVBS2: |