drivers/gpu/drm/amd/display/dc/basics/fixpt31_32.c - linux/torvalds/linux - Git at Google

 /*
  * Copyright 2012-15 Advanced Micro Devices, Inc.
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
  * to deal in the Software without restriction, including without limitation
  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  * and/or sell copies of the Software, and to permit persons to whom the
  * Software is furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  * OTHER DEALINGS IN THE SOFTWARE.
  *
  * Authors: AMD
  *
  */

 #include "dm_services.h"
 #include "include/fixed31_32.h"

 static inline unsigned long long abs_i64(
 	long long arg)
 {
 	if (arg > 0)
 		return (unsigned long long)arg;
 	else
 		return (unsigned long long)(-arg);
 }

 /*
  * @brief
  * result = dividend / divisor
  * *remainder = dividend % divisor
  */
 static inline unsigned long long complete_integer_division_u64(
 	unsigned long long dividend,
 	unsigned long long divisor,
 	unsigned long long *remainder)
 {
 	unsigned long long result;

 	ASSERT(divisor);

 	result = div64_u64_rem(dividend, divisor, remainder);

 	return result;
 }


 #define FRACTIONAL_PART_MASK \
 	((1ULL << FIXED31_32_BITS_PER_FRACTIONAL_PART) - 1)

 #define GET_INTEGER_PART(x) \
 	((x) >> FIXED31_32_BITS_PER_FRACTIONAL_PART)

 #define GET_FRACTIONAL_PART(x) \
 	(FRACTIONAL_PART_MASK & (x))

 struct fixed31_32 dc_fixpt_from_fraction(long long numerator, long long denominator)
 {
 	struct fixed31_32 res;

 	bool arg1_negative = numerator < 0;
 	bool arg2_negative = denominator < 0;

 	unsigned long long arg1_value = arg1_negative ? -numerator : numerator;
 	unsigned long long arg2_value = arg2_negative ? -denominator : denominator;

 	unsigned long long remainder;

 	/* determine integer part */

 	unsigned long long res_value = complete_integer_division_u64(
 		arg1_value, arg2_value, &remainder);

 	ASSERT(res_value <= LONG_MAX);

 	/* determine fractional part */
 	{
 		unsigned int i = FIXED31_32_BITS_PER_FRACTIONAL_PART;

 		do {
 			remainder <<= 1;

 			res_value <<= 1;

 			if (remainder >= arg2_value) {
 				res_value |= 1;
 				remainder -= arg2_value;
 			}
 		} while (--i != 0);
 	}

 	/* round up LSB */
 	{
 		unsigned long long summand = (remainder << 1) >= arg2_value;

 		ASSERT(res_value <= LLONG_MAX - summand);

 		res_value += summand;
 	}

 	res.value = (long long)res_value;

 	if (arg1_negative ^ arg2_negative)
 		res.value = -res.value;

 	return res;
 }

 struct fixed31_32 dc_fixpt_mul(struct fixed31_32 arg1, struct fixed31_32 arg2)
 {
 	struct fixed31_32 res;

 	bool arg1_negative = arg1.value < 0;
 	bool arg2_negative = arg2.value < 0;

 	unsigned long long arg1_value = arg1_negative ? -arg1.value : arg1.value;
 	unsigned long long arg2_value = arg2_negative ? -arg2.value : arg2.value;

 	unsigned long long arg1_int = GET_INTEGER_PART(arg1_value);
 	unsigned long long arg2_int = GET_INTEGER_PART(arg2_value);

 	unsigned long long arg1_fra = GET_FRACTIONAL_PART(arg1_value);
 	unsigned long long arg2_fra = GET_FRACTIONAL_PART(arg2_value);

 	unsigned long long tmp;

 	res.value = arg1_int * arg2_int;

 	ASSERT(res.value <= LONG_MAX);

 	res.value <<= FIXED31_32_BITS_PER_FRACTIONAL_PART;

 	tmp = arg1_int * arg2_fra;

 	ASSERT(tmp <= (unsigned long long)(LLONG_MAX - res.value));

 	res.value += tmp;

 	tmp = arg2_int * arg1_fra;

 	ASSERT(tmp <= (unsigned long long)(LLONG_MAX - res.value));

 	res.value += tmp;

 	tmp = arg1_fra * arg2_fra;

 	tmp = (tmp >> FIXED31_32_BITS_PER_FRACTIONAL_PART) +
 		(tmp >= (unsigned long long)dc_fixpt_half.value);

 	ASSERT(tmp <= (unsigned long long)(LLONG_MAX - res.value));

 	res.value += tmp;

 	if (arg1_negative ^ arg2_negative)
 		res.value = -res.value;

 	return res;
 }

 struct fixed31_32 dc_fixpt_sqr(struct fixed31_32 arg)
 {
 	struct fixed31_32 res;

 	unsigned long long arg_value = abs_i64(arg.value);

 	unsigned long long arg_int = GET_INTEGER_PART(arg_value);

 	unsigned long long arg_fra = GET_FRACTIONAL_PART(arg_value);

 	unsigned long long tmp;

 	res.value = arg_int * arg_int;

 	ASSERT(res.value <= LONG_MAX);

 	res.value <<= FIXED31_32_BITS_PER_FRACTIONAL_PART;

 	tmp = arg_int * arg_fra;

 	ASSERT(tmp <= (unsigned long long)(LLONG_MAX - res.value));

 	res.value += tmp;

 	ASSERT(tmp <= (unsigned long long)(LLONG_MAX - res.value));

 	res.value += tmp;

 	tmp = arg_fra * arg_fra;

 	tmp = (tmp >> FIXED31_32_BITS_PER_FRACTIONAL_PART) +
 		(tmp >= (unsigned long long)dc_fixpt_half.value);

 	ASSERT(tmp <= (unsigned long long)(LLONG_MAX - res.value));

 	res.value += tmp;

 	return res;
 }

 struct fixed31_32 dc_fixpt_recip(struct fixed31_32 arg)
 {
 	/*
 	 * @note
 	 * Good idea to use Newton's method
 	 */

 	ASSERT(arg.value);

 	return dc_fixpt_from_fraction(
 		dc_fixpt_one.value,
 		arg.value);
 }

 struct fixed31_32 dc_fixpt_sinc(struct fixed31_32 arg)
 {
 	struct fixed31_32 square;

 	struct fixed31_32 res = dc_fixpt_one;

 	int n = 27;

 	struct fixed31_32 arg_norm = arg;

 	if (dc_fixpt_le(
 		dc_fixpt_two_pi,
 		dc_fixpt_abs(arg))) {
 		arg_norm = dc_fixpt_sub(
 			arg_norm,
 			dc_fixpt_mul_int(
 				dc_fixpt_two_pi,
 				(int)div64_s64(
 					arg_norm.value,
 					dc_fixpt_two_pi.value)));
 	}

 	square = dc_fixpt_sqr(arg_norm);

 	do {
 		res = dc_fixpt_sub(
 			dc_fixpt_one,
 			dc_fixpt_div_int(
 				dc_fixpt_mul(
 					square,
 					res),
 				n * (n - 1)));

 		n -= 2;
 	} while (n > 2);

 	if (arg.value != arg_norm.value)
 		res = dc_fixpt_div(
 			dc_fixpt_mul(res, arg_norm),
 			arg);

 	return res;
 }

 struct fixed31_32 dc_fixpt_sin(struct fixed31_32 arg)
 {
 	return dc_fixpt_mul(
 		arg,
 		dc_fixpt_sinc(arg));
 }

 struct fixed31_32 dc_fixpt_cos(struct fixed31_32 arg)
 {
 	/* TODO implement argument normalization */

 	const struct fixed31_32 square = dc_fixpt_sqr(arg);

 	struct fixed31_32 res = dc_fixpt_one;

 	int n = 26;

 	do {
 		res = dc_fixpt_sub(
 			dc_fixpt_one,
 			dc_fixpt_div_int(
 				dc_fixpt_mul(
 					square,
 					res),
 				n * (n - 1)));

 		n -= 2;
 	} while (n != 0);

 	return res;
 }

 /*
  * @brief
  * result = exp(arg),
  * where abs(arg) < 1
  *
  * Calculated as Taylor series.
  */
 static struct fixed31_32 fixed31_32_exp_from_taylor_series(struct fixed31_32 arg)
 {
 	unsigned int n = 9;

 	struct fixed31_32 res = dc_fixpt_from_fraction(
 		n + 2,
 		n + 1);
 	/* TODO find correct res */

 	ASSERT(dc_fixpt_lt(arg, dc_fixpt_one));

 	do
 		res = dc_fixpt_add(
 			dc_fixpt_one,
 			dc_fixpt_div_int(
 				dc_fixpt_mul(
 					arg,
 					res),
 				n));
 	while (--n != 1);

 	return dc_fixpt_add(
 		dc_fixpt_one,
 		dc_fixpt_mul(
 			arg,
 			res));
 }

 struct fixed31_32 dc_fixpt_exp(struct fixed31_32 arg)
 {
 	/*
 	 * @brief
 	 * Main equation is:
 	 * exp(x) = exp(r + m * ln(2)) = (1 << m) * exp(r),
 	 * where m = round(x / ln(2)), r = x - m * ln(2)
 	 */

 	if (dc_fixpt_le(
 		dc_fixpt_ln2_div_2,
 		dc_fixpt_abs(arg))) {
 		int m = dc_fixpt_round(
 			dc_fixpt_div(
 				arg,
 				dc_fixpt_ln2));

 		struct fixed31_32 r = dc_fixpt_sub(
 			arg,
 			dc_fixpt_mul_int(
 				dc_fixpt_ln2,
 				m));

 		ASSERT(m != 0);

 		ASSERT(dc_fixpt_lt(
 			dc_fixpt_abs(r),
 			dc_fixpt_one));

 		if (m > 0)
 			return dc_fixpt_shl(
 				fixed31_32_exp_from_taylor_series(r),
 				(unsigned char)m);
 		else
 			return dc_fixpt_div_int(
 				fixed31_32_exp_from_taylor_series(r),
 				1LL << -m);
 	} else if (arg.value != 0)
 		return fixed31_32_exp_from_taylor_series(arg);
 	else
 		return dc_fixpt_one;
 }

 struct fixed31_32 dc_fixpt_log(struct fixed31_32 arg)
 {
 	struct fixed31_32 res = dc_fixpt_neg(dc_fixpt_one);
 	/* TODO improve 1st estimation */

 	struct fixed31_32 error;

 	ASSERT(arg.value > 0);
 	/* TODO if arg is negative, return NaN */
 	/* TODO if arg is zero, return -INF */

 	do {
 		struct fixed31_32 res1 = dc_fixpt_add(
 			dc_fixpt_sub(
 				res,
 				dc_fixpt_one),
 			dc_fixpt_div(
 				arg,
 				dc_fixpt_exp(res)));

 		error = dc_fixpt_sub(
 			res,
 			res1);

 		res = res1;
 		/* TODO determine max_allowed_error based on quality of exp() */
 	} while (abs_i64(error.value) > 100ULL);

 	return res;
 }


 /* this function is a generic helper to translate fixed point value to
  * specified integer format that will consist of integer_bits integer part and
  * fractional_bits fractional part. For example it is used in
  * dc_fixpt_u2d19 to receive 2 bits integer part and 19 bits fractional
  * part in 32 bits. It is used in hw programming (scaler)
  */

 static inline unsigned int ux_dy(
 	long long value,
 	unsigned int integer_bits,
 	unsigned int fractional_bits)
 {
 	/* 1. create mask of integer part */
 	unsigned int result = (1 << integer_bits) - 1;
 	/* 2. mask out fractional part */
 	unsigned int fractional_part = FRACTIONAL_PART_MASK & value;
 	/* 3. shrink fixed point integer part to be of integer_bits width*/
 	result &= GET_INTEGER_PART(value);
 	/* 4. make space for fractional part to be filled in after integer */
 	result <<= fractional_bits;
 	/* 5. shrink fixed point fractional part to of fractional_bits width*/
 	fractional_part >>= FIXED31_32_BITS_PER_FRACTIONAL_PART - fractional_bits;
 	/* 6. merge the result */
 	return result | fractional_part;
 }

 static inline unsigned int clamp_ux_dy(
 	long long value,
 	unsigned int integer_bits,
 	unsigned int fractional_bits,
 	unsigned int min_clamp)
 {
 	unsigned int truncated_val = ux_dy(value, integer_bits, fractional_bits);

 	if (value >= (1LL << (integer_bits + FIXED31_32_BITS_PER_FRACTIONAL_PART)))
 		return (1 << (integer_bits + fractional_bits)) - 1;
 	else if (truncated_val > min_clamp)
 		return truncated_val;
 	else
 		return min_clamp;
 }

 unsigned int dc_fixpt_u4d19(struct fixed31_32 arg)
 {
 	return ux_dy(arg.value, 4, 19);
 }

 unsigned int dc_fixpt_u3d19(struct fixed31_32 arg)
 {
 	return ux_dy(arg.value, 3, 19);
 }

 unsigned int dc_fixpt_u2d19(struct fixed31_32 arg)
 {
 	return ux_dy(arg.value, 2, 19);
 }

 unsigned int dc_fixpt_u0d19(struct fixed31_32 arg)
 {
 	return ux_dy(arg.value, 0, 19);
 }

 unsigned int dc_fixpt_clamp_u0d14(struct fixed31_32 arg)
 {
 	return clamp_ux_dy(arg.value, 0, 14, 1);
 }

 unsigned int dc_fixpt_clamp_u0d10(struct fixed31_32 arg)
 {
 	return clamp_ux_dy(arg.value, 0, 10, 1);
 }

 int dc_fixpt_s4d19(struct fixed31_32 arg)
 {
 	if (arg.value < 0)
 		return -(int)ux_dy(dc_fixpt_abs(arg).value, 4, 19);
 	else
 		return ux_dy(arg.value, 4, 19);
 }
	/*
	* Copyright 2012-15 Advanced Micro Devices, Inc.
	*
	* Permission is hereby granted, free of charge, to any person obtaining a
	* copy of this software and associated documentation files (the "Software"),
	* to deal in the Software without restriction, including without limitation
	* the rights to use, copy, modify, merge, publish, distribute, sublicense,
	* and/or sell copies of the Software, and to permit persons to whom the
	* Software is furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice shall be included in
	* all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	* THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
	* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
	* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
	* OTHER DEALINGS IN THE SOFTWARE.
	*
	* Authors: AMD
	*
	*/

	#include "dm_services.h"
	#include "include/fixed31_32.h"

	static inline unsigned long long abs_i64(
	long long arg)
	{
	if (arg > 0)
	return (unsigned long long)arg;
	else
	return (unsigned long long)(-arg);
	}

	/*
	* @brief
	* result = dividend / divisor
	* *remainder = dividend % divisor
	*/
	static inline unsigned long long complete_integer_division_u64(
	unsigned long long dividend,
	unsigned long long divisor,
	unsigned long long *remainder)
	{
	unsigned long long result;

	ASSERT(divisor);

	result = div64_u64_rem(dividend, divisor, remainder);

	return result;
	}


	#define FRACTIONAL_PART_MASK \
	((1ULL << FIXED31_32_BITS_PER_FRACTIONAL_PART) - 1)

	#define GET_INTEGER_PART(x) \
	((x) >> FIXED31_32_BITS_PER_FRACTIONAL_PART)

	#define GET_FRACTIONAL_PART(x) \
	(FRACTIONAL_PART_MASK & (x))

	struct fixed31_32 dc_fixpt_from_fraction(long long numerator, long long denominator)
	{
	struct fixed31_32 res;

	bool arg1_negative = numerator < 0;
	bool arg2_negative = denominator < 0;

	unsigned long long arg1_value = arg1_negative ? -numerator : numerator;
	unsigned long long arg2_value = arg2_negative ? -denominator : denominator;

	unsigned long long remainder;

	/* determine integer part */

	unsigned long long res_value = complete_integer_division_u64(
	arg1_value, arg2_value, &remainder);

	ASSERT(res_value <= LONG_MAX);

	/* determine fractional part */
	{
	unsigned int i = FIXED31_32_BITS_PER_FRACTIONAL_PART;

	do {
	remainder <<= 1;

	res_value <<= 1;

	if (remainder >= arg2_value) {
	res_value \|= 1;
	remainder -= arg2_value;
	}
	} while (--i != 0);
	}

	/* round up LSB */
	{
	unsigned long long summand = (remainder << 1) >= arg2_value;

	ASSERT(res_value <= LLONG_MAX - summand);

	res_value += summand;
	}

	res.value = (long long)res_value;

	if (arg1_negative ^ arg2_negative)
	res.value = -res.value;

	return res;
	}

	struct fixed31_32 dc_fixpt_mul(struct fixed31_32 arg1, struct fixed31_32 arg2)
	{
	struct fixed31_32 res;

	bool arg1_negative = arg1.value < 0;
	bool arg2_negative = arg2.value < 0;

	unsigned long long arg1_value = arg1_negative ? -arg1.value : arg1.value;
	unsigned long long arg2_value = arg2_negative ? -arg2.value : arg2.value;

	unsigned long long arg1_int = GET_INTEGER_PART(arg1_value);
	unsigned long long arg2_int = GET_INTEGER_PART(arg2_value);

	unsigned long long arg1_fra = GET_FRACTIONAL_PART(arg1_value);
	unsigned long long arg2_fra = GET_FRACTIONAL_PART(arg2_value);

	unsigned long long tmp;

	res.value = arg1_int * arg2_int;

	ASSERT(res.value <= LONG_MAX);

	res.value <<= FIXED31_32_BITS_PER_FRACTIONAL_PART;

	tmp = arg1_int * arg2_fra;

	ASSERT(tmp <= (unsigned long long)(LLONG_MAX - res.value));

	res.value += tmp;

	tmp = arg2_int * arg1_fra;

	ASSERT(tmp <= (unsigned long long)(LLONG_MAX - res.value));

	res.value += tmp;

	tmp = arg1_fra * arg2_fra;

	tmp = (tmp >> FIXED31_32_BITS_PER_FRACTIONAL_PART) +
	(tmp >= (unsigned long long)dc_fixpt_half.value);

	ASSERT(tmp <= (unsigned long long)(LLONG_MAX - res.value));

	res.value += tmp;

	if (arg1_negative ^ arg2_negative)
	res.value = -res.value;

	return res;
	}

	struct fixed31_32 dc_fixpt_sqr(struct fixed31_32 arg)
	{
	struct fixed31_32 res;

	unsigned long long arg_value = abs_i64(arg.value);

	unsigned long long arg_int = GET_INTEGER_PART(arg_value);

	unsigned long long arg_fra = GET_FRACTIONAL_PART(arg_value);

	unsigned long long tmp;

	res.value = arg_int * arg_int;

	ASSERT(res.value <= LONG_MAX);

	res.value <<= FIXED31_32_BITS_PER_FRACTIONAL_PART;

	tmp = arg_int * arg_fra;

	ASSERT(tmp <= (unsigned long long)(LLONG_MAX - res.value));

	res.value += tmp;

	ASSERT(tmp <= (unsigned long long)(LLONG_MAX - res.value));

	res.value += tmp;

	tmp = arg_fra * arg_fra;

	tmp = (tmp >> FIXED31_32_BITS_PER_FRACTIONAL_PART) +
	(tmp >= (unsigned long long)dc_fixpt_half.value);

	ASSERT(tmp <= (unsigned long long)(LLONG_MAX - res.value));

	res.value += tmp;

	return res;
	}

	struct fixed31_32 dc_fixpt_recip(struct fixed31_32 arg)
	{
	/*
	* @note
	* Good idea to use Newton's method
	*/

	ASSERT(arg.value);

	return dc_fixpt_from_fraction(
	dc_fixpt_one.value,
	arg.value);
	}

	struct fixed31_32 dc_fixpt_sinc(struct fixed31_32 arg)
	{
	struct fixed31_32 square;

	struct fixed31_32 res = dc_fixpt_one;

	int n = 27;

	struct fixed31_32 arg_norm = arg;

	if (dc_fixpt_le(
	dc_fixpt_two_pi,
	dc_fixpt_abs(arg))) {
	arg_norm = dc_fixpt_sub(
	arg_norm,
	dc_fixpt_mul_int(
	dc_fixpt_two_pi,
	(int)div64_s64(
	arg_norm.value,
	dc_fixpt_two_pi.value)));
	}

	square = dc_fixpt_sqr(arg_norm);

	do {
	res = dc_fixpt_sub(
	dc_fixpt_one,
	dc_fixpt_div_int(
	dc_fixpt_mul(
	square,
	res),
	n * (n - 1)));

	n -= 2;
	} while (n > 2);

	if (arg.value != arg_norm.value)
	res = dc_fixpt_div(
	dc_fixpt_mul(res, arg_norm),
	arg);

	return res;
	}

	struct fixed31_32 dc_fixpt_sin(struct fixed31_32 arg)
	{
	return dc_fixpt_mul(
	arg,
	dc_fixpt_sinc(arg));
	}

	struct fixed31_32 dc_fixpt_cos(struct fixed31_32 arg)
	{
	/* TODO implement argument normalization */

	const struct fixed31_32 square = dc_fixpt_sqr(arg);

	struct fixed31_32 res = dc_fixpt_one;

	int n = 26;

	do {
	res = dc_fixpt_sub(
	dc_fixpt_one,
	dc_fixpt_div_int(
	dc_fixpt_mul(
	square,
	res),
	n * (n - 1)));

	n -= 2;
	} while (n != 0);

	return res;
	}

	/*
	* @brief
	* result = exp(arg),
	* where abs(arg) < 1
	*
	* Calculated as Taylor series.
	*/
	static struct fixed31_32 fixed31_32_exp_from_taylor_series(struct fixed31_32 arg)
	{
	unsigned int n = 9;

	struct fixed31_32 res = dc_fixpt_from_fraction(
	n + 2,
	n + 1);
	/* TODO find correct res */

	ASSERT(dc_fixpt_lt(arg, dc_fixpt_one));

	do
	res = dc_fixpt_add(
	dc_fixpt_one,
	dc_fixpt_div_int(
	dc_fixpt_mul(
	arg,
	res),
	n));
	while (--n != 1);

	return dc_fixpt_add(
	dc_fixpt_one,
	dc_fixpt_mul(
	arg,
	res));
	}

	struct fixed31_32 dc_fixpt_exp(struct fixed31_32 arg)
	{
	/*
	* @brief
	* Main equation is:
	* exp(x) = exp(r + m * ln(2)) = (1 << m) * exp(r),
	* where m = round(x / ln(2)), r = x - m * ln(2)
	*/

	if (dc_fixpt_le(
	dc_fixpt_ln2_div_2,
	dc_fixpt_abs(arg))) {
	int m = dc_fixpt_round(
	dc_fixpt_div(
	arg,
	dc_fixpt_ln2));

	struct fixed31_32 r = dc_fixpt_sub(
	arg,
	dc_fixpt_mul_int(
	dc_fixpt_ln2,
	m));

	ASSERT(m != 0);

	ASSERT(dc_fixpt_lt(
	dc_fixpt_abs(r),
	dc_fixpt_one));

	if (m > 0)
	return dc_fixpt_shl(
	fixed31_32_exp_from_taylor_series(r),
	(unsigned char)m);
	else
	return dc_fixpt_div_int(
	fixed31_32_exp_from_taylor_series(r),
	1LL << -m);
	} else if (arg.value != 0)
	return fixed31_32_exp_from_taylor_series(arg);
	else
	return dc_fixpt_one;
	}

	struct fixed31_32 dc_fixpt_log(struct fixed31_32 arg)
	{
	struct fixed31_32 res = dc_fixpt_neg(dc_fixpt_one);
	/* TODO improve 1st estimation */

	struct fixed31_32 error;

	ASSERT(arg.value > 0);
	/* TODO if arg is negative, return NaN */
	/* TODO if arg is zero, return -INF */

	do {
	struct fixed31_32 res1 = dc_fixpt_add(
	dc_fixpt_sub(
	res,
	dc_fixpt_one),
	dc_fixpt_div(
	arg,
	dc_fixpt_exp(res)));

	error = dc_fixpt_sub(
	res,
	res1);

	res = res1;
	/* TODO determine max_allowed_error based on quality of exp() */
	} while (abs_i64(error.value) > 100ULL);

	return res;
	}


	/* this function is a generic helper to translate fixed point value to
	* specified integer format that will consist of integer_bits integer part and
	* fractional_bits fractional part. For example it is used in
	* dc_fixpt_u2d19 to receive 2 bits integer part and 19 bits fractional
	* part in 32 bits. It is used in hw programming (scaler)
	*/

	static inline unsigned int ux_dy(
	long long value,
	unsigned int integer_bits,
	unsigned int fractional_bits)
	{
	/* 1. create mask of integer part */
	unsigned int result = (1 << integer_bits) - 1;
	/* 2. mask out fractional part */
	unsigned int fractional_part = FRACTIONAL_PART_MASK & value;
	/* 3. shrink fixed point integer part to be of integer_bits width*/
	result &= GET_INTEGER_PART(value);
	/* 4. make space for fractional part to be filled in after integer */
	result <<= fractional_bits;
	/* 5. shrink fixed point fractional part to of fractional_bits width*/
	fractional_part >>= FIXED31_32_BITS_PER_FRACTIONAL_PART - fractional_bits;
	/* 6. merge the result */
	return result \| fractional_part;
	}

	static inline unsigned int clamp_ux_dy(
	long long value,
	unsigned int integer_bits,
	unsigned int fractional_bits,
	unsigned int min_clamp)
	{
	unsigned int truncated_val = ux_dy(value, integer_bits, fractional_bits);

	if (value >= (1LL << (integer_bits + FIXED31_32_BITS_PER_FRACTIONAL_PART)))
	return (1 << (integer_bits + fractional_bits)) - 1;
	else if (truncated_val > min_clamp)
	return truncated_val;
	else
	return min_clamp;
	}

	unsigned int dc_fixpt_u4d19(struct fixed31_32 arg)
	{
	return ux_dy(arg.value, 4, 19);
	}

	unsigned int dc_fixpt_u3d19(struct fixed31_32 arg)
	{
	return ux_dy(arg.value, 3, 19);
	}

	unsigned int dc_fixpt_u2d19(struct fixed31_32 arg)
	{
	return ux_dy(arg.value, 2, 19);
	}

	unsigned int dc_fixpt_u0d19(struct fixed31_32 arg)
	{
	return ux_dy(arg.value, 0, 19);
	}

	unsigned int dc_fixpt_clamp_u0d14(struct fixed31_32 arg)
	{
	return clamp_ux_dy(arg.value, 0, 14, 1);
	}

	unsigned int dc_fixpt_clamp_u0d10(struct fixed31_32 arg)
	{
	return clamp_ux_dy(arg.value, 0, 10, 1);
	}

	int dc_fixpt_s4d19(struct fixed31_32 arg)
	{
	if (arg.value < 0)
	return -(int)ux_dy(dc_fixpt_abs(arg).value, 4, 19);
	else
	return ux_dy(arg.value, 4, 19);
	}