.. kernel-doc:: include/linux/log2.h
:internal:
-Integer power Functions
------------------------
+Integer log and power Functions
+-------------------------------
+
+.. kernel-doc:: include/linux/int_log.h
+ :export:
.. kernel-doc:: lib/math/int_pow.c
:export:
Digital TV Common functions
---------------------------
-Math functions
-~~~~~~~~~~~~~~
-
-Provide some commonly-used math functions, usually required in order to
-estimate signal strength and signal to noise measurements in dB.
-
-.. kernel-doc:: include/media/dvb_math.h
-
-
DVB devices
~~~~~~~~~~~
dvb-core-objs := dvbdev.o dmxdev.o dvb_demux.o \
dvb_ca_en50221.o dvb_frontend.o \
- $(dvb-net-y) dvb_ringbuffer.o $(dvb-vb2-y) dvb_math.o
+ $(dvb-net-y) dvb_ringbuffer.o $(dvb-vb2-y)
obj-$(CONFIG_DVB_CORE) += dvb-core.o
+++ /dev/null
-/*
- * dvb-math provides some complex fixed-point math
- * operations shared between the dvb related stuff
- *
- * Copyright (C) 2006 Christoph Pfister (christophpfister@gmail.com)
- *
- * This library is free software; you can redistribute it and/or modify
- * it under the terms of the GNU Lesser General Public License as
- * published by the Free Software Foundation; either version 2.1 of
- * the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU Lesser General Public License for more details.
- */
-
-#include <linux/bitops.h>
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <asm/bug.h>
-#include <media/dvb_math.h>
-
-static const unsigned short logtable[256] = {
- 0x0000, 0x0171, 0x02e0, 0x044e, 0x05ba, 0x0725, 0x088e, 0x09f7,
- 0x0b5d, 0x0cc3, 0x0e27, 0x0f8a, 0x10eb, 0x124b, 0x13aa, 0x1508,
- 0x1664, 0x17bf, 0x1919, 0x1a71, 0x1bc8, 0x1d1e, 0x1e73, 0x1fc6,
- 0x2119, 0x226a, 0x23ba, 0x2508, 0x2656, 0x27a2, 0x28ed, 0x2a37,
- 0x2b80, 0x2cc8, 0x2e0f, 0x2f54, 0x3098, 0x31dc, 0x331e, 0x345f,
- 0x359f, 0x36de, 0x381b, 0x3958, 0x3a94, 0x3bce, 0x3d08, 0x3e41,
- 0x3f78, 0x40af, 0x41e4, 0x4319, 0x444c, 0x457f, 0x46b0, 0x47e1,
- 0x4910, 0x4a3f, 0x4b6c, 0x4c99, 0x4dc5, 0x4eef, 0x5019, 0x5142,
- 0x526a, 0x5391, 0x54b7, 0x55dc, 0x5700, 0x5824, 0x5946, 0x5a68,
- 0x5b89, 0x5ca8, 0x5dc7, 0x5ee5, 0x6003, 0x611f, 0x623a, 0x6355,
- 0x646f, 0x6588, 0x66a0, 0x67b7, 0x68ce, 0x69e4, 0x6af8, 0x6c0c,
- 0x6d20, 0x6e32, 0x6f44, 0x7055, 0x7165, 0x7274, 0x7383, 0x7490,
- 0x759d, 0x76aa, 0x77b5, 0x78c0, 0x79ca, 0x7ad3, 0x7bdb, 0x7ce3,
- 0x7dea, 0x7ef0, 0x7ff6, 0x80fb, 0x81ff, 0x8302, 0x8405, 0x8507,
- 0x8608, 0x8709, 0x8809, 0x8908, 0x8a06, 0x8b04, 0x8c01, 0x8cfe,
- 0x8dfa, 0x8ef5, 0x8fef, 0x90e9, 0x91e2, 0x92db, 0x93d2, 0x94ca,
- 0x95c0, 0x96b6, 0x97ab, 0x98a0, 0x9994, 0x9a87, 0x9b7a, 0x9c6c,
- 0x9d5e, 0x9e4f, 0x9f3f, 0xa02e, 0xa11e, 0xa20c, 0xa2fa, 0xa3e7,
- 0xa4d4, 0xa5c0, 0xa6ab, 0xa796, 0xa881, 0xa96a, 0xaa53, 0xab3c,
- 0xac24, 0xad0c, 0xadf2, 0xaed9, 0xafbe, 0xb0a4, 0xb188, 0xb26c,
- 0xb350, 0xb433, 0xb515, 0xb5f7, 0xb6d9, 0xb7ba, 0xb89a, 0xb97a,
- 0xba59, 0xbb38, 0xbc16, 0xbcf4, 0xbdd1, 0xbead, 0xbf8a, 0xc065,
- 0xc140, 0xc21b, 0xc2f5, 0xc3cf, 0xc4a8, 0xc580, 0xc658, 0xc730,
- 0xc807, 0xc8de, 0xc9b4, 0xca8a, 0xcb5f, 0xcc34, 0xcd08, 0xcddc,
- 0xceaf, 0xcf82, 0xd054, 0xd126, 0xd1f7, 0xd2c8, 0xd399, 0xd469,
- 0xd538, 0xd607, 0xd6d6, 0xd7a4, 0xd872, 0xd93f, 0xda0c, 0xdad9,
- 0xdba5, 0xdc70, 0xdd3b, 0xde06, 0xded0, 0xdf9a, 0xe063, 0xe12c,
- 0xe1f5, 0xe2bd, 0xe385, 0xe44c, 0xe513, 0xe5d9, 0xe69f, 0xe765,
- 0xe82a, 0xe8ef, 0xe9b3, 0xea77, 0xeb3b, 0xebfe, 0xecc1, 0xed83,
- 0xee45, 0xef06, 0xefc8, 0xf088, 0xf149, 0xf209, 0xf2c8, 0xf387,
- 0xf446, 0xf505, 0xf5c3, 0xf680, 0xf73e, 0xf7fb, 0xf8b7, 0xf973,
- 0xfa2f, 0xfaea, 0xfba5, 0xfc60, 0xfd1a, 0xfdd4, 0xfe8e, 0xff47
-};
-
-unsigned int intlog2(u32 value)
-{
- /**
- * returns: log2(value) * 2^24
- * wrong result if value = 0 (log2(0) is undefined)
- */
- unsigned int msb;
- unsigned int logentry;
- unsigned int significand;
- unsigned int interpolation;
-
- if (unlikely(value == 0)) {
- WARN_ON(1);
- return 0;
- }
-
- /* first detect the msb (count begins at 0) */
- msb = fls(value) - 1;
-
- /**
- * now we use a logtable after the following method:
- *
- * log2(2^x * y) * 2^24 = x * 2^24 + log2(y) * 2^24
- * where x = msb and therefore 1 <= y < 2
- * first y is determined by shifting the value left
- * so that msb is bit 31
- * 0x00231f56 -> 0x8C7D5800
- * the result is y * 2^31 -> "significand"
- * then the highest 9 bits are used for a table lookup
- * the highest bit is discarded because it's always set
- * the highest nine bits in our example are 100011000
- * so we would use the entry 0x18
- */
- significand = value << (31 - msb);
- logentry = (significand >> 23) & 0xff;
-
- /**
- * last step we do is interpolation because of the
- * limitations of the log table the error is that part of
- * the significand which isn't used for lookup then we
- * compute the ratio between the error and the next table entry
- * and interpolate it between the log table entry used and the
- * next one the biggest error possible is 0x7fffff
- * (in our example it's 0x7D5800)
- * needed value for next table entry is 0x800000
- * so the interpolation is
- * (error / 0x800000) * (logtable_next - logtable_current)
- * in the implementation the division is moved to the end for
- * better accuracy there is also an overflow correction if
- * logtable_next is 256
- */
- interpolation = ((significand & 0x7fffff) *
- ((logtable[(logentry + 1) & 0xff] -
- logtable[logentry]) & 0xffff)) >> 15;
-
- /* now we return the result */
- return ((msb << 24) + (logtable[logentry] << 8) + interpolation);
-}
-EXPORT_SYMBOL(intlog2);
-
-unsigned int intlog10(u32 value)
-{
- /**
- * returns: log10(value) * 2^24
- * wrong result if value = 0 (log10(0) is undefined)
- */
- u64 log;
-
- if (unlikely(value == 0)) {
- WARN_ON(1);
- return 0;
- }
-
- log = intlog2(value);
-
- /**
- * we use the following method:
- * log10(x) = log2(x) * log10(2)
- */
-
- return (log * 646456993) >> 31;
-}
-EXPORT_SYMBOL(intlog10);
#define AF9013_PRIV_H
#include <media/dvb_frontend.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include "af9013.h"
#include <linux/firmware.h>
#include <linux/i2c-mux.h>
#include <linux/math64.h>
#include <linux/regmap.h>
#include <linux/kernel.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
struct reg_val {
u32 reg;
#include <linux/dvb/version.h>
#include <media/dvb_frontend.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include "cxd2820r.h"
#include <linux/gpio/driver.h> /* For gpio_chip */
#include <linux/math64.h>
#include <linux/dynamic_debug.h>
#include <linux/kernel.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include <media/dvb_frontend.h>
#include "cxd2841er.h"
#include "cxd2841er_priv.h"
#include "cxd2880_tnrdmd_dvbt2.h"
#include "cxd2880_tnrdmd_dvbt2_mon.h"
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
static const int ref_dbm_1000[4][8] = {
{-96000, -95000, -94000, -93000, -92000, -92000, -98000, -97000},
#include "cxd2880_tnrdmd_dvbt.h"
#include "cxd2880_tnrdmd_dvbt_mon.h"
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
static const int ref_dbm_1000[3][5] = {
{-93000, -91000, -90000, -89000, -88000},
#include <linux/spi/spi.h>
#include <media/dvb_frontend.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include "cxd2880.h"
#include "cxd2880_tnrdmd_mon.h"
#include <linux/mutex.h>
#include <asm/div64.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include <media/dvb_frontend.h>
#include "dib7000p.h"
#include <linux/mutex.h>
#include <asm/div64.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include <media/dvb_frontend.h>
#include <linux/i2c.h>
#include <linux/mutex.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include <media/dvb_frontend.h>
#include "dib9000.h"
#include <media/dvb_frontend.h>
#include "drxk.h"
#include "drxk_hard.h"
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
static int power_down_dvbt(struct drxk_state *state, bool set_power_mode);
static int power_down_qam(struct drxk_state *state);
#include <asm/div64.h>
#include <linux/dvb/frontend.h>
#include <linux/slab.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include "lgdt3305.h"
static int debug;
#include <asm/div64.h>
#include <linux/kernel.h>
#include <linux/dvb/frontend.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include "lgdt3306a.h"
#include <linux/i2c-mux.h>
#include <asm/byteorder.h>
#include <media/dvb_frontend.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include "lgdt330x_priv.h"
#include "lgdt330x.h"
#include <media/dvb_frontend.h>
#include "m88ds3103.h"
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include <linux/firmware.h>
#include <linux/i2c-mux.h>
#include <linux/regmap.h>
#include <linux/gpio/consumer.h>
#include <linux/of_device.h>
#include <linux/regmap.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include "mn88443x.h"
#define MN88472_PRIV_H
#include <media/dvb_frontend.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include "mn88472.h"
#include <linux/firmware.h>
#include <linux/regmap.h>
#define MN88473_PRIV_H
#include <media/dvb_frontend.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include "mn88473.h"
#include <linux/math64.h>
#include <linux/firmware.h>
#include <linux/slab.h>
#include <asm/byteorder.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include <media/dvb_frontend.h>
#include "or51132.h"
#include <linux/slab.h>
#include <asm/byteorder.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include <media/dvb_frontend.h>
#include "or51211.h"
#define RTL2830_PRIV_H
#include <media/dvb_frontend.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include "rtl2830.h"
#include <linux/i2c-mux.h>
#include <linux/math64.h>
#include <linux/bitops.h>
#include <media/dvb_frontend.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include "rtl2832.h"
struct rtl2832_dev {
#include <linux/regmap.h>
#include <media/dvb_frontend.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include "si2165_priv.h"
#include "si2165.h"
#include <linux/slab.h>
#include <linux/i2c.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include "stv0367.h"
#include "stv0367_defs.h"
#include <linux/kernel.h>
#include <linux/math64.h>
#include <linux/dvb/frontend.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include "tc90522.h"
#define TC90522_I2C_THRU_REG 0xfe
#include <linux/math64.h>
#include <asm/div64.h>
#include <media/dvb_frontend.h>
-#include <media/dvb_math.h>
+#include <linux/int_log.h>
#include "tda10048.h"
#define TDA10048_DEFAULT_FIRMWARE "dvb-fe-tda10048-1.0.fw"
--- /dev/null
+/*
+ * Provides fixed-point logarithm operations.
+ *
+ * Copyright (C) 2006 Christoph Pfister (christophpfister@gmail.com)
+ *
+ * This library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ */
+
+#ifndef __LINUX_INT_LOG_H
+#define __LINUX_INT_LOG_H
+
+#include <linux/types.h>
+
+/**
+ * intlog2 - computes log2 of a value; the result is shifted left by 24 bits
+ *
+ * @value: The value (must be != 0)
+ *
+ * to use rational values you can use the following method:
+ *
+ * intlog2(value) = intlog2(value * 2^x) - x * 2^24
+ *
+ * Some usecase examples:
+ *
+ * intlog2(8) will give 3 << 24 = 3 * 2^24
+ *
+ * intlog2(9) will give 3 << 24 + ... = 3.16... * 2^24
+ *
+ * intlog2(1.5) = intlog2(3) - 2^24 = 0.584... * 2^24
+ *
+ *
+ * return: log2(value) * 2^24
+ */
+extern unsigned int intlog2(u32 value);
+
+/**
+ * intlog10 - computes log10 of a value; the result is shifted left by 24 bits
+ *
+ * @value: The value (must be != 0)
+ *
+ * to use rational values you can use the following method:
+ *
+ * intlog10(value) = intlog10(value * 10^x) - x * 2^24
+ *
+ * An usecase example:
+ *
+ * intlog10(1000) will give 3 << 24 = 3 * 2^24
+ *
+ * due to the implementation intlog10(1000) might be not exactly 3 * 2^24
+ *
+ * look at intlog2 for similar examples
+ *
+ * return: log10(value) * 2^24
+ */
+extern unsigned int intlog10(u32 value);
+
+#endif
+++ /dev/null
-/*
- * dvb-math provides some complex fixed-point math
- * operations shared between the dvb related stuff
- *
- * Copyright (C) 2006 Christoph Pfister (christophpfister@gmail.com)
- *
- * This library is free software; you can redistribute it and/or modify
- * it under the terms of the GNU Lesser General Public License as
- * published by the Free Software Foundation; either version 2.1 of
- * the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU Lesser General Public License for more details.
- */
-
-#ifndef __DVB_MATH_H
-#define __DVB_MATH_H
-
-#include <linux/types.h>
-
-/**
- * intlog2 - computes log2 of a value; the result is shifted left by 24 bits
- *
- * @value: The value (must be != 0)
- *
- * to use rational values you can use the following method:
- *
- * intlog2(value) = intlog2(value * 2^x) - x * 2^24
- *
- * Some usecase examples:
- *
- * intlog2(8) will give 3 << 24 = 3 * 2^24
- *
- * intlog2(9) will give 3 << 24 + ... = 3.16... * 2^24
- *
- * intlog2(1.5) = intlog2(3) - 2^24 = 0.584... * 2^24
- *
- *
- * return: log2(value) * 2^24
- */
-extern unsigned int intlog2(u32 value);
-
-/**
- * intlog10 - computes log10 of a value; the result is shifted left by 24 bits
- *
- * @value: The value (must be != 0)
- *
- * to use rational values you can use the following method:
- *
- * intlog10(value) = intlog10(value * 10^x) - x * 2^24
- *
- * An usecase example:
- *
- * intlog10(1000) will give 3 << 24 = 3 * 2^24
- *
- * due to the implementation intlog10(1000) might be not exactly 3 * 2^24
- *
- * look at intlog2 for similar examples
- *
- * return: log10(value) * 2^24
- */
-extern unsigned int intlog10(u32 value);
-
-#endif
# SPDX-License-Identifier: GPL-2.0-only
-obj-y += div64.o gcd.o lcm.o int_pow.o int_sqrt.o reciprocal_div.o
+obj-y += div64.o gcd.o lcm.o int_log.o int_pow.o int_sqrt.o reciprocal_div.o
obj-$(CONFIG_CORDIC) += cordic.o
obj-$(CONFIG_PRIME_NUMBERS) += prime_numbers.o
--- /dev/null
+/*
+ * Provides fixed-point logarithm operations.
+ *
+ * Copyright (C) 2006 Christoph Pfister (christophpfister@gmail.com)
+ *
+ * This library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ */
+
+#include <linux/bitops.h>
+#include <linux/export.h>
+#include <linux/int_log.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+
+#include <asm/bug.h>
+
+static const unsigned short logtable[256] = {
+ 0x0000, 0x0171, 0x02e0, 0x044e, 0x05ba, 0x0725, 0x088e, 0x09f7,
+ 0x0b5d, 0x0cc3, 0x0e27, 0x0f8a, 0x10eb, 0x124b, 0x13aa, 0x1508,
+ 0x1664, 0x17bf, 0x1919, 0x1a71, 0x1bc8, 0x1d1e, 0x1e73, 0x1fc6,
+ 0x2119, 0x226a, 0x23ba, 0x2508, 0x2656, 0x27a2, 0x28ed, 0x2a37,
+ 0x2b80, 0x2cc8, 0x2e0f, 0x2f54, 0x3098, 0x31dc, 0x331e, 0x345f,
+ 0x359f, 0x36de, 0x381b, 0x3958, 0x3a94, 0x3bce, 0x3d08, 0x3e41,
+ 0x3f78, 0x40af, 0x41e4, 0x4319, 0x444c, 0x457f, 0x46b0, 0x47e1,
+ 0x4910, 0x4a3f, 0x4b6c, 0x4c99, 0x4dc5, 0x4eef, 0x5019, 0x5142,
+ 0x526a, 0x5391, 0x54b7, 0x55dc, 0x5700, 0x5824, 0x5946, 0x5a68,
+ 0x5b89, 0x5ca8, 0x5dc7, 0x5ee5, 0x6003, 0x611f, 0x623a, 0x6355,
+ 0x646f, 0x6588, 0x66a0, 0x67b7, 0x68ce, 0x69e4, 0x6af8, 0x6c0c,
+ 0x6d20, 0x6e32, 0x6f44, 0x7055, 0x7165, 0x7274, 0x7383, 0x7490,
+ 0x759d, 0x76aa, 0x77b5, 0x78c0, 0x79ca, 0x7ad3, 0x7bdb, 0x7ce3,
+ 0x7dea, 0x7ef0, 0x7ff6, 0x80fb, 0x81ff, 0x8302, 0x8405, 0x8507,
+ 0x8608, 0x8709, 0x8809, 0x8908, 0x8a06, 0x8b04, 0x8c01, 0x8cfe,
+ 0x8dfa, 0x8ef5, 0x8fef, 0x90e9, 0x91e2, 0x92db, 0x93d2, 0x94ca,
+ 0x95c0, 0x96b6, 0x97ab, 0x98a0, 0x9994, 0x9a87, 0x9b7a, 0x9c6c,
+ 0x9d5e, 0x9e4f, 0x9f3f, 0xa02e, 0xa11e, 0xa20c, 0xa2fa, 0xa3e7,
+ 0xa4d4, 0xa5c0, 0xa6ab, 0xa796, 0xa881, 0xa96a, 0xaa53, 0xab3c,
+ 0xac24, 0xad0c, 0xadf2, 0xaed9, 0xafbe, 0xb0a4, 0xb188, 0xb26c,
+ 0xb350, 0xb433, 0xb515, 0xb5f7, 0xb6d9, 0xb7ba, 0xb89a, 0xb97a,
+ 0xba59, 0xbb38, 0xbc16, 0xbcf4, 0xbdd1, 0xbead, 0xbf8a, 0xc065,
+ 0xc140, 0xc21b, 0xc2f5, 0xc3cf, 0xc4a8, 0xc580, 0xc658, 0xc730,
+ 0xc807, 0xc8de, 0xc9b4, 0xca8a, 0xcb5f, 0xcc34, 0xcd08, 0xcddc,
+ 0xceaf, 0xcf82, 0xd054, 0xd126, 0xd1f7, 0xd2c8, 0xd399, 0xd469,
+ 0xd538, 0xd607, 0xd6d6, 0xd7a4, 0xd872, 0xd93f, 0xda0c, 0xdad9,
+ 0xdba5, 0xdc70, 0xdd3b, 0xde06, 0xded0, 0xdf9a, 0xe063, 0xe12c,
+ 0xe1f5, 0xe2bd, 0xe385, 0xe44c, 0xe513, 0xe5d9, 0xe69f, 0xe765,
+ 0xe82a, 0xe8ef, 0xe9b3, 0xea77, 0xeb3b, 0xebfe, 0xecc1, 0xed83,
+ 0xee45, 0xef06, 0xefc8, 0xf088, 0xf149, 0xf209, 0xf2c8, 0xf387,
+ 0xf446, 0xf505, 0xf5c3, 0xf680, 0xf73e, 0xf7fb, 0xf8b7, 0xf973,
+ 0xfa2f, 0xfaea, 0xfba5, 0xfc60, 0xfd1a, 0xfdd4, 0xfe8e, 0xff47,
+};
+
+unsigned int intlog2(u32 value)
+{
+ /**
+ * returns: log2(value) * 2^24
+ * wrong result if value = 0 (log2(0) is undefined)
+ */
+ unsigned int msb;
+ unsigned int logentry;
+ unsigned int significand;
+ unsigned int interpolation;
+
+ if (unlikely(value == 0)) {
+ WARN_ON(1);
+ return 0;
+ }
+
+ /* first detect the msb (count begins at 0) */
+ msb = fls(value) - 1;
+
+ /**
+ * now we use a logtable after the following method:
+ *
+ * log2(2^x * y) * 2^24 = x * 2^24 + log2(y) * 2^24
+ * where x = msb and therefore 1 <= y < 2
+ * first y is determined by shifting the value left
+ * so that msb is bit 31
+ * 0x00231f56 -> 0x8C7D5800
+ * the result is y * 2^31 -> "significand"
+ * then the highest 9 bits are used for a table lookup
+ * the highest bit is discarded because it's always set
+ * the highest nine bits in our example are 100011000
+ * so we would use the entry 0x18
+ */
+ significand = value << (31 - msb);
+ logentry = (significand >> 23) & 0xff;
+
+ /**
+ * last step we do is interpolation because of the
+ * limitations of the log table the error is that part of
+ * the significand which isn't used for lookup then we
+ * compute the ratio between the error and the next table entry
+ * and interpolate it between the log table entry used and the
+ * next one the biggest error possible is 0x7fffff
+ * (in our example it's 0x7D5800)
+ * needed value for next table entry is 0x800000
+ * so the interpolation is
+ * (error / 0x800000) * (logtable_next - logtable_current)
+ * in the implementation the division is moved to the end for
+ * better accuracy there is also an overflow correction if
+ * logtable_next is 256
+ */
+ interpolation = ((significand & 0x7fffff) *
+ ((logtable[(logentry + 1) & 0xff] -
+ logtable[logentry]) & 0xffff)) >> 15;
+
+ /* now we return the result */
+ return ((msb << 24) + (logtable[logentry] << 8) + interpolation);
+}
+EXPORT_SYMBOL(intlog2);
+
+unsigned int intlog10(u32 value)
+{
+ /**
+ * returns: log10(value) * 2^24
+ * wrong result if value = 0 (log10(0) is undefined)
+ */
+ u64 log;
+
+ if (unlikely(value == 0)) {
+ WARN_ON(1);
+ return 0;
+ }
+
+ log = intlog2(value);
+
+ /**
+ * we use the following method:
+ * log10(x) = log2(x) * log10(2)
+ */
+
+ return (log * 646456993) >> 31;
+}
+EXPORT_SYMBOL(intlog10);
projects / platform / kernel / linux-rpi.git / commitdiff