Commit 38670189 authored Aug 29, 2015 by Joerg Riechardt Committed by Mauro Carvalho Chehab Nov 23, 2016

[media] stv090x: use lookup tables for carrier/noise ratio



The stv090x driver uses the lookup table for signal strength already,
with this patch we use the lookup tables for carrier/noise ratio as well.
This has the advantage, that values for DVB-S and DVB-S2 are now
corresponding, while before they were way off. The values are now
proportional to real carrier/noise ratio, while before they were
corresponding to register values. So now applications are able to give
the user real carrier/noise ratio.

Because the output has to be within 0x0000...0xFFFF the three negative
values for DVB-S2 are omitted. This is no significant loss, because
reception is lost at 7.5 dB already (TT S2-1600, Cine S2), so the
negative values are not really important, and also for DVB-S they don´t
exist.

Signed-off-by: Joerg Riechardt <j.riechardt@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

parent 8ccd22db

drivers/media/dvb-frontends/stv090x.c

+10 −6

Original line number	Diff line number	Diff line
		@@ -3692,9 +3692,12 @@ static int stv090x_read_cnr(struct dvb_frontend fe, u16 cnr)
		}
		val /= 16;
		last = ARRAY_SIZE(stv090x_s2cn_tab) - 1;
		div = stv090x_s2cn_tab[0].read -
		stv090x_s2cn_tab[last].read;
		cnr = 0xFFFF - ((val 0xFFFF) / div);
		div = stv090x_s2cn_tab[last].real -
		stv090x_s2cn_tab[3].real;
		val = stv090x_table_lookup(stv090x_s2cn_tab, last, val);
		if (val < 0)
		val = 0;
		cnr = val 0xFFFF / div;
		}
		break;

		@@ -3714,9 +3717,10 @@ static int stv090x_read_cnr(struct dvb_frontend fe, u16 cnr)
		}
		val /= 16;
		last = ARRAY_SIZE(stv090x_s1cn_tab) - 1;
		div = stv090x_s1cn_tab[0].read -
		stv090x_s1cn_tab[last].read;
		cnr = 0xFFFF - ((val 0xFFFF) / div);
		div = stv090x_s1cn_tab[last].real -
		stv090x_s1cn_tab[0].real;
		val = stv090x_table_lookup(stv090x_s1cn_tab, last, val);
		cnr = val 0xFFFF / div;
		}
		break;
		default: