diff options
author | Jean Delvare <khali@linux-fr.org> | 2012-02-12 13:03:03 -0500 |
---|---|---|
committer | Mauro Carvalho Chehab <mchehab@redhat.com> | 2012-03-08 06:54:42 -0500 |
commit | 06302ffbb470359c8cbcf1ee8b057d6930300f90 (patch) | |
tree | d2f8ad2bf7b0bf2650eecc1d9643c94464f07944 /drivers/media/dvb/frontends/cx22702.c | |
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/media/dvb/frontends/cx22702.c')
-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 faba82485086..edc8eafc5c09 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, | |||
502 | u16 *signal_strength) | 502 | u16 *signal_strength) |
503 | { | 503 | { |
504 | struct cx22702_state *state = fe->demodulator_priv; | 504 | struct cx22702_state *state = fe->demodulator_priv; |
505 | u8 reg23; | ||
505 | 506 | ||
506 | u16 rs_ber; | 507 | /* |
507 | rs_ber = cx22702_readreg(state, 0x23); | 508 | * Experience suggests that the strength signal register works as |
508 | *signal_strength = (rs_ber << 8) | rs_ber; | 509 | * follows: |
510 | * - In the absence of signal, value is 0xff. | ||
511 | * - In the presence of a weak signal, bit 7 is set, not sure what | ||
512 | * the lower 7 bits mean. | ||
513 | * - In the presence of a strong signal, the register holds a 7-bit | ||
514 | * value (bit 7 is cleared), with greater values standing for | ||
515 | * weaker signals. | ||
516 | */ | ||
517 | reg23 = cx22702_readreg(state, 0x23); | ||
518 | if (reg23 & 0x80) { | ||
519 | *signal_strength = 0; | ||
520 | } else { | ||
521 | reg23 = ~reg23 & 0x7f; | ||
522 | /* Scale to 16 bit */ | ||
523 | *signal_strength = (reg23 << 9) | (reg23 << 2) | (reg23 >> 5); | ||
524 | } | ||
509 | 525 | ||
510 | return 0; | 526 | return 0; |
511 | } | 527 | } |