1/* 2 * SpanDSP - a series of DSP components for telephony 3 * 4 * fir.h - General telephony FIR routines 5 * 6 * Written by Steve Underwood <steveu@coppice.org> 7 * 8 * Copyright (C) 2002 Steve Underwood 9 * 10 * All rights reserved. 11 * 12 * This program is free software; you can redistribute it and/or modify 13 * it under the terms of the GNU General Public License version 2, as 14 * published by the Free Software Foundation. 15 * 16 * This program is distributed in the hope that it will be useful, 17 * but WITHOUT ANY WARRANTY; without even the implied warranty of 18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 19 * GNU General Public License for more details. 20 * 21 * You should have received a copy of the GNU General Public License 22 * along with this program; if not, write to the Free Software 23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 24 */ 25 26#if !defined(_FIR_H_) 27#define _FIR_H_ 28 29/* 30 Blackfin NOTES & IDEAS: 31 32 A simple dot product function is used to implement the filter. This performs 33 just one MAC/cycle which is inefficient but was easy to implement as a first 34 pass. The current Blackfin code also uses an unrolled form of the filter 35 history to avoid 0 length hardware loop issues. This is wasteful of 36 memory. 37 38 Ideas for improvement: 39 40 1/ Rewrite filter for dual MAC inner loop. The issue here is handling 41 history sample offsets that are 16 bit aligned - the dual MAC needs 42 32 bit aligmnent. There are some good examples in libbfdsp. 43 44 2/ Use the hardware circular buffer facility tohalve memory usage. 45 46 3/ Consider using internal memory. 47 48 Using less memory might also improve speed as cache misses will be 49 reduced. A drop in MIPs and memory approaching 50% should be 50 possible. 51 52 The foreground and background filters currenlty use a total of 53 about 10 MIPs/ch as measured with speedtest.c on a 256 TAP echo 54 can. 55*/ 56 57/* 58 * 16 bit integer FIR descriptor. This defines the working state for a single 59 * instance of an FIR filter using 16 bit integer coefficients. 60 */ 61struct fir16_state_t { 62 int taps; 63 int curr_pos; 64 const int16_t *coeffs; 65 int16_t *history; 66}; 67 68/* 69 * 32 bit integer FIR descriptor. This defines the working state for a single 70 * instance of an FIR filter using 32 bit integer coefficients, and filtering 71 * 16 bit integer data. 72 */ 73struct fir32_state_t { 74 int taps; 75 int curr_pos; 76 const int32_t *coeffs; 77 int16_t *history; 78}; 79 80/* 81 * Floating point FIR descriptor. This defines the working state for a single 82 * instance of an FIR filter using floating point coefficients and data. 83 */ 84struct fir_float_state_t { 85 int taps; 86 int curr_pos; 87 const float *coeffs; 88 float *history; 89}; 90 91static inline const int16_t *fir16_create(struct fir16_state_t *fir, 92 const int16_t *coeffs, int taps) 93{ 94 fir->taps = taps; 95 fir->curr_pos = taps - 1; 96 fir->coeffs = coeffs; 97#if defined(__bfin__) 98 fir->history = kcalloc(2 * taps, sizeof(int16_t), GFP_KERNEL); 99#else 100 fir->history = kcalloc(taps, sizeof(int16_t), GFP_KERNEL); 101#endif 102 return fir->history; 103} 104 105static inline void fir16_flush(struct fir16_state_t *fir) 106{ 107#if defined(__bfin__) 108 memset(fir->history, 0, 2 * fir->taps * sizeof(int16_t)); 109#else 110 memset(fir->history, 0, fir->taps * sizeof(int16_t)); 111#endif 112} 113 114static inline void fir16_free(struct fir16_state_t *fir) 115{ 116 kfree(fir->history); 117} 118 119#ifdef __bfin__ 120static inline int32_t dot_asm(short *x, short *y, int len) 121{ 122 int dot; 123 124 len--; 125 126 __asm__("I0 = %1;\n\t" 127 "I1 = %2;\n\t" 128 "A0 = 0;\n\t" 129 "R0.L = W[I0++] || R1.L = W[I1++];\n\t" 130 "LOOP dot%= LC0 = %3;\n\t" 131 "LOOP_BEGIN dot%=;\n\t" 132 "A0 += R0.L * R1.L (IS) || R0.L = W[I0++] || R1.L = W[I1++];\n\t" 133 "LOOP_END dot%=;\n\t" 134 "A0 += R0.L*R1.L (IS);\n\t" 135 "R0 = A0;\n\t" 136 "%0 = R0;\n\t" 137 : "=&d"(dot) 138 : "a"(x), "a"(y), "a"(len) 139 : "I0", "I1", "A1", "A0", "R0", "R1" 140 ); 141 142 return dot; 143} 144#endif 145 146static inline int16_t fir16(struct fir16_state_t *fir, int16_t sample) 147{ 148 int32_t y; 149#if defined(__bfin__) 150 fir->history[fir->curr_pos] = sample; 151 fir->history[fir->curr_pos + fir->taps] = sample; 152 y = dot_asm((int16_t *) fir->coeffs, &fir->history[fir->curr_pos], 153 fir->taps); 154#else 155 int i; 156 int offset1; 157 int offset2; 158 159 fir->history[fir->curr_pos] = sample; 160 161 offset2 = fir->curr_pos; 162 offset1 = fir->taps - offset2; 163 y = 0; 164 for (i = fir->taps - 1; i >= offset1; i--) 165 y += fir->coeffs[i] * fir->history[i - offset1]; 166 for (; i >= 0; i--) 167 y += fir->coeffs[i] * fir->history[i + offset2]; 168#endif 169 if (fir->curr_pos <= 0) 170 fir->curr_pos = fir->taps; 171 fir->curr_pos--; 172 return (int16_t) (y >> 15); 173} 174 175static inline const int16_t *fir32_create(struct fir32_state_t *fir, 176 const int32_t *coeffs, int taps) 177{ 178 fir->taps = taps; 179 fir->curr_pos = taps - 1; 180 fir->coeffs = coeffs; 181 fir->history = kcalloc(taps, sizeof(int16_t), GFP_KERNEL); 182 return fir->history; 183} 184 185static inline void fir32_flush(struct fir32_state_t *fir) 186{ 187 memset(fir->history, 0, fir->taps * sizeof(int16_t)); 188} 189 190static inline void fir32_free(struct fir32_state_t *fir) 191{ 192 kfree(fir->history); 193} 194 195static inline int16_t fir32(struct fir32_state_t *fir, int16_t sample) 196{ 197 int i; 198 int32_t y; 199 int offset1; 200 int offset2; 201 202 fir->history[fir->curr_pos] = sample; 203 offset2 = fir->curr_pos; 204 offset1 = fir->taps - offset2; 205 y = 0; 206 for (i = fir->taps - 1; i >= offset1; i--) 207 y += fir->coeffs[i] * fir->history[i - offset1]; 208 for (; i >= 0; i--) 209 y += fir->coeffs[i] * fir->history[i + offset2]; 210 if (fir->curr_pos <= 0) 211 fir->curr_pos = fir->taps; 212 fir->curr_pos--; 213 return (int16_t) (y >> 15); 214} 215 216#endif 217