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 */
61 struct 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 */
73 struct 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 */
84 struct fir_float_state_t {
85 int taps;
86 int curr_pos;
87 const float *coeffs;
88 float *history;
89 };
90
fir16_create(struct fir16_state_t * fir,const int16_t * coeffs,int taps)91 static 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
fir16_flush(struct fir16_state_t * fir)105 static 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
fir16_free(struct fir16_state_t * fir)114 static inline void fir16_free(struct fir16_state_t *fir)
115 {
116 kfree(fir->history);
117 }
118
119 #ifdef __bfin__
dot_asm(short * x,short * y,int len)120 static 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
fir16(struct fir16_state_t * fir,int16_t sample)146 static 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
fir32_create(struct fir32_state_t * fir,const int32_t * coeffs,int taps)175 static 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
fir32_flush(struct fir32_state_t * fir)185 static inline void fir32_flush(struct fir32_state_t *fir)
186 {
187 memset(fir->history, 0, fir->taps * sizeof(int16_t));
188 }
189
fir32_free(struct fir32_state_t * fir)190 static inline void fir32_free(struct fir32_state_t *fir)
191 {
192 kfree(fir->history);
193 }
194
fir32(struct fir32_state_t * fir,int16_t sample)195 static 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