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