diff options
| author | Jean Delvare <khali@linux-fr.org> | 2012-02-12 15:03:03 -0300 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab@redhat.com> | 2012-03-08 08:54:42 -0300 |
| commit | 06302ffbb470359c8cbcf1ee8b057d6930300f90 (patch) | |
| tree | d2f8ad2bf7b0bf2650eecc1d9643c94464f07944 /drivers | |
| parent | 6c5637e4eda58292f7d9ee6ee0b1f9aa4b0a7e7f (diff) | |
[media] cx22702: Fix signal strength
The signal strength value returned is not quite correct, it decreases
when I increase the gain of my antenna, and vice versa. It also
doesn't span over the whole 0x0000-0xffff range. Compute a value which
at least increases when signal strength increases, and spans the whole
allowed range.
In practice I get 67% with my antenna fully amplified and 51% with
no amplification. This is close enough to what I get on my other
DVB-T adapter with the same antenna.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Steven Toth <stoth@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/media/dvb/frontends/cx22702.c | 22 |
1 files changed, 19 insertions, 3 deletions
diff --git a/drivers/media/dvb/frontends/cx22702.c b/drivers/media/dvb/frontends/cx22702.c index faba8248508..edc8eafc5c0 100644 --- a/drivers/media/dvb/frontends/cx22702.c +++ b/drivers/media/dvb/frontends/cx22702.c @@ -502,10 +502,26 @@ static int cx22702_read_signal_strength(struct dvb_frontend *fe, u16 *signal_strength) { struct cx22702_state *state = fe->demodulator_priv; + u8 reg23; - u16 rs_ber; - rs_ber = cx22702_readreg(state, 0x23); - *signal_strength = (rs_ber << 8) | rs_ber; + /* + * Experience suggests that the strength signal register works as + * follows: + * - In the absence of signal, value is 0xff. + * - In the presence of a weak signal, bit 7 is set, not sure what + * the lower 7 bits mean. + * - In the presence of a strong signal, the register holds a 7-bit + * value (bit 7 is cleared), with greater values standing for + * weaker signals. + */ + reg23 = cx22702_readreg(state, 0x23); + if (reg23 & 0x80) { + *signal_strength = 0; + } else { + reg23 = ~reg23 & 0x7f; + /* Scale to 16 bit */ + *signal_strength = (reg23 << 9) | (reg23 << 2) | (reg23 >> 5); + } return 0; } |