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[media] dvb-frontends/cxd2841er: improved snr reporting

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On DVB-T/T2 at least, SNR might be reported as >2500dB, which not only is
just wrong but also ridiculous, so fix this by improving the conversion
of the register value.

The INTLOG10X100 function/macro and the way the values are converted were
both taken from DD's cxd2843 driver.

Signed-off-by: Daniel Scheller <d.scheller@gmx.net>
Acked-by: Abylay Ospan <aospan@netup.ru>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
This commit is contained in:
Daniel Scheller 2017-04-09 16:38:24 -03:00 committed by Mauro Carvalho Chehab
parent bf51bbb044
commit df61f828d4
1 changed files with 4 additions and 3 deletions
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7
drivers/media/dvb-frontends/cxd2841er.c
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@ -38,6 +38,8 @@
#define MAX_WRITE_REGSIZE 16 #define MAX_WRITE_REGSIZE 16
#define LOG2_E_100X 144 #define LOG2_E_100X 144
#define INTLOG10X100(x) ((u32) (((u64) intlog10(x) * 100) >> 24))
/* DVB-C constellation */ /* DVB-C constellation */
enum sony_dvbc_constellation_t { enum sony_dvbc_constellation_t {
SONY_DVBC_CONSTELLATION_16QAM, SONY_DVBC_CONSTELLATION_16QAM,
@ -1817,7 +1819,7 @@ static int cxd2841er_read_snr_t(struct cxd2841er_priv *priv, u32 *snr)
} }
if (reg > 4996) if (reg > 4996)
reg = 4996; reg = 4996;
*snr = 10000 * ((intlog10(reg) - intlog10(5350 - reg)) >> 24) + 28500; *snr = 100 * ((INTLOG10X100(reg) - INTLOG10X100(5350 - reg)) + 285);
return 0; return 0;
} }
@ -1846,8 +1848,7 @@ static int cxd2841er_read_snr_t2(struct cxd2841er_priv *priv, u32 *snr)
} }
if (reg > 10876) if (reg > 10876)
reg = 10876; reg = 10876;
*snr = 10000 * ((intlog10(reg) - *snr = 100 * ((INTLOG10X100(reg) - INTLOG10X100(12600 - reg)) + 320);
intlog10(12600 - reg)) >> 24) + 32000;
return 0; return 0;
} }