/* SPDX-License-Identifier: GPL-2.0-only *//* * SpanDSP - a series of DSP components for telephony * * fir.h - General telephony FIR routines * * Written by Steve Underwood <steveu@coppice.org> * * Copyright (C) 2002 Steve Underwood * * All rights reserved. */ #if !defined(_FIR_H_)#define _FIR_H_ /*   Ideas for improvement:    1/ Rewrite filter for dual MAC inner loop.  The issue here is handling   history sample offsets that are 16 bit aligned - the dual MAC needs   32 bit aligmnent.  There are some good examples in libbfdsp.    2/ Use the hardware circular buffer facility tohalve memory usage.    3/ Consider using internal memory.    Using less memory might also improve speed as cache misses will be   reduced. A drop in MIPs and memory approaching 50% should be   possible.    The foreground and background filters currenlty use a total of   about 10 MIPs/ch as measured with speedtest.c on a 256 TAP echo   can.*/ /* * 16 bit integer FIR descriptor. This defines the working state for a single * instance of an FIR filter using 16 bit integer coefficients. */struct fir16_state_t {	int taps;	int curr_pos;	const int16_t *coeffs;	int16_t *history;}; /* * 32 bit integer FIR descriptor. This defines the working state for a single * instance of an FIR filter using 32 bit integer coefficients, and filtering * 16 bit integer data. */struct fir32_state_t {	int taps;	int curr_pos;	const int32_t *coeffs;	int16_t *history;}; /* * Floating point FIR descriptor. This defines the working state for a single * instance of an FIR filter using floating point coefficients and data. */struct fir_float_state_t {	int taps;	int curr_pos;	const float *coeffs;	float *history;}; static inline const int16_t *fir16_create(struct fir16_state_t *fir,					      const int16_t *coeffs, int taps){	fir->taps = taps;	fir->curr_pos = taps - 1;	fir->coeffs = coeffs;	fir->history = kcalloc(taps, sizeof(int16_t), GFP_KERNEL);	return fir->history;} static inline void fir16_flush(struct fir16_state_t *fir){	memset(fir->history, 0, fir->taps * sizeof(int16_t));} static inline void fir16_free(struct fir16_state_t *fir){	kfree(fir->history);} static inline int16_t fir16(struct fir16_state_t *fir, int16_t sample){	int32_t y;	int i;	int offset1;	int offset2; 	fir->history[fir->curr_pos] = sample; 	offset2 = fir->curr_pos;	offset1 = fir->taps - offset2;	y = 0;	for (i = fir->taps - 1; i >= offset1; i--)		y += fir->coeffs[i] * fir->history[i - offset1];	for (; i >= 0; i--)		y += fir->coeffs[i] * fir->history[i + offset2];	if (fir->curr_pos <= 0)		fir->curr_pos = fir->taps;	fir->curr_pos--;	return (int16_t) (y >> 15);} static inline const int16_t *fir32_create(struct fir32_state_t *fir,					      const int32_t *coeffs, int taps){	fir->taps = taps;	fir->curr_pos = taps - 1;	fir->coeffs = coeffs;	fir->history = kcalloc(taps, sizeof(int16_t), GFP_KERNEL);	return fir->history;} static inline void fir32_flush(struct fir32_state_t *fir){	memset(fir->history, 0, fir->taps * sizeof(int16_t));} static inline void fir32_free(struct fir32_state_t *fir){	kfree(fir->history);} static inline int16_t fir32(struct fir32_state_t *fir, int16_t sample){	int i;	int32_t y;	int offset1;	int offset2; 	fir->history[fir->curr_pos] = sample;	offset2 = fir->curr_pos;	offset1 = fir->taps - offset2;	y = 0;	for (i = fir->taps - 1; i >= offset1; i--)		y += fir->coeffs[i] * fir->history[i - offset1];	for (; i >= 0; i--)		y += fir->coeffs[i] * fir->history[i + offset2];	if (fir->curr_pos <= 0)		fir->curr_pos = fir->taps;	fir->curr_pos--;	return (int16_t) (y >> 15);} #endif