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Commit 313a7dfb authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab
Browse files

[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: default avatarMauro Carvalho Chehab <mchehab@s-opensource.com>
parent d12b791e

drivers/media/dvb-frontends/cxd2841er.c

+10 −7
Original line number Diff line number Diff line
@@ -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: