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[media] drxk_hard: don't re-implement log10

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X-Patchwork-Delegate: mchehab@redhat.com
Log10 routine is already defined at dvb_math.h and provides a good
enough approximation for 100 x log10(). So, instead of reinventing
the wheel, use the already existing function.
While here, don't use CamelCase on the function name.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Mauro Carvalho Chehab 2013-04-28 11:47:43 -03:00
parent 7df272563a
commit b5e9eb6f52
1 changed files with 8 additions and 96 deletions
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104
drivers/media/dvb-frontends/drxk_hard.c
View file

@ -34,6 +34,7 @@
#include "dvb_frontend.h"
#include "drxk.h"
#include "drxk_hard.h"
#include "dvb_math.h"
static int PowerDownDVBT(struct drxk_state *state, bool setPowerMode);
static int PowerDownQAM(struct drxk_state *state);
@ -201,98 +202,9 @@ static inline u32 Frac28a(u32 a, u32 c)
return Q1;
}
static u32 Log10Times100(u32 x)
static inline u32 log10times100(u32 value)
{
static const u8 scale = 15;
static const u8 indexWidth = 5;
u8 i = 0;
u32 y = 0;
u32 d = 0;
u32 k = 0;
u32 r = 0;
/*
log2lut[n] = (1<<scale) * 200 * log2(1.0 + ((1.0/(1<<INDEXWIDTH)) * n))
0 <= n < ((1<<INDEXWIDTH)+1)
*/
static const u32 log2lut[] = {
0, /* 0.000000 */
290941, /* 290941.300628 */
573196, /* 573196.476418 */
847269, /* 847269.179851 */
1113620, /* 1113620.489452 */
1372674, /* 1372673.576986 */
1624818, /* 1624817.752104 */
1870412, /* 1870411.981536 */
2109788, /* 2109787.962654 */
2343253, /* 2343252.817465 */
2571091, /* 2571091.461923 */
2793569, /* 2793568.696416 */
3010931, /* 3010931.055901 */
3223408, /* 3223408.452106 */
3431216, /* 3431215.635215 */
3634553, /* 3634553.498355 */
3833610, /* 3833610.244726 */
4028562, /* 4028562.434393 */
4219576, /* 4219575.925308 */
4406807, /* 4406806.721144 */
4590402, /* 4590401.736809 */
4770499, /* 4770499.491025 */
4947231, /* 4947230.734179 */
5120719, /* 5120719.018555 */
5291081, /* 5291081.217197 */
5458428, /* 5458427.996830 */
5622864, /* 5622864.249668 */
5784489, /* 5784489.488298 */
5943398, /* 5943398.207380 */
6099680, /* 6099680.215452 */
6253421, /* 6253420.939751 */
6404702, /* 6404701.706649 */
6553600, /* 6553600.000000 */
};
if (x == 0)
return 0;
/* Scale x (normalize) */
/* computing y in log(x/y) = log(x) - log(y) */
if ((x & ((0xffffffff) << (scale + 1))) == 0) {
for (k = scale; k > 0; k--) {
if (x & (((u32) 1) << scale))
break;
x <<= 1;
}
} else {
for (k = scale; k < 31; k++) {
if ((x & (((u32) (-1)) << (scale + 1))) == 0)
break;
x >>= 1;
}
}
/*
Now x has binary point between bit[scale] and bit[scale-1]
and 1.0 <= x < 2.0 */
/* correction for divison: log(x) = log(x/y)+log(y) */
y = k * ((((u32) 1) << scale) * 200);
/* remove integer part */
x &= ((((u32) 1) << scale) - 1);
/* get index */
i = (u8) (x >> (scale - indexWidth));
/* compute delta (x - a) */
d = x & ((((u32) 1) << (scale - indexWidth)) - 1);
/* compute log, multiplication (d* (..)) must be within range ! */
y += log2lut[i] +
((d * (log2lut[i + 1] - log2lut[i])) >> (scale - indexWidth));
/* Conver to log10() */
y /= 108853; /* (log2(10) << scale) */
r = (y >> 1);
/* rounding */
if (y & ((u32) 1))
r++;
return r;
return (100L * intlog10(value)) >> 24;
}
/****************************************************************************/
@ -2530,8 +2442,8 @@ static int GetQAMSignalToNoise(struct drxk_state *state,
}
if (qamSlErrPower > 0) {
qamSlMer = Log10Times100(qamSlSigPower) -
Log10Times100((u32) qamSlErrPower);
qamSlMer = log10times100(qamSlSigPower) -
log10times100((u32) qamSlErrPower);
}
*pSignalToNoise = qamSlMer;
@ -2620,12 +2532,12 @@ static int GetDVBTSignalToNoise(struct drxk_state *state,
*/
/* log(x) x = 9bits * 9bits->18 bits */
a = Log10Times100(EqRegTdTpsPwrOfs *
a = log10times100(EqRegTdTpsPwrOfs *
EqRegTdTpsPwrOfs);
/* log(x) x = 16bits * 7bits->23 bits */
b = Log10Times100(EqRegTdReqSmbCnt * tpsCnt);
b = log10times100(EqRegTdReqSmbCnt * tpsCnt);
/* log(x) x = (16bits + 16bits) << 15 ->32 bits */
c = Log10Times100(SqrErrIQ);
c = log10times100(SqrErrIQ);
iMER = a + b - c;
}