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[media] au8522: Calculate signal strength shown as percentage from SNR up to 35dB

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As done first in lgdt330x.c, calculate signal strength from SNR up to 35dB
Even though the SNR can go higher than 35dB, there is some comfort factor
in having a range of strong signals that can show at 100%

Signed-off-by: Michael Krufky <mkrufky@kernellabs.com>
Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Steven Toth <stoth@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Michael Krufky 2011-10-31 08:11:00 -03:00 committed by Mauro Carvalho Chehab
parent 49a0513c1f
commit 5279b1ff36
1 changed files with 30 additions and 1 deletions
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31
drivers/media/dvb/frontends/au8522_dig.c
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@ -862,7 +862,36 @@ static int au8522_read_snr(struct dvb_frontend *fe, u16 *snr)
static int au8522_read_signal_strength(struct dvb_frontend *fe,
u16 *signal_strength)
{
return au8522_read_snr(fe, signal_strength);
/* borrowed from lgdt330x.c
*
* Calculate strength from SNR up to 35dB
* Even though the SNR can go higher than 35dB,
* there is some comfort factor in having a range of
* strong signals that can show at 100%
*/
u16 snr;
u32 tmp;
int ret = au8522_read_snr(fe, &snr);
*signal_strength = 0;
if (0 == ret) {
/* The following calculation method was chosen
* purely for the sake of code re-use from the
* other demod drivers that use this method */
/* Convert from SNR in dB * 10 to 8.24 fixed-point */
tmp = (snr * ((1 << 24) / 10));
/* Convert from 8.24 fixed-point to
* scale the range 0 - 35*2^24 into 0 - 65535*/
if (tmp >= 8960 * 0x10000)
*signal_strength = 0xffff;
else
*signal_strength = tmp / 8960;
}
return ret;
}
static int au8522_read_ucblocks(struct dvb_frontend *fe, u32 *ucblocks)