1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
|
/*
* 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.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2, as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#if !defined(_FIR_H_)
#define _FIR_H_
/*
Blackfin NOTES & IDEAS:
A simple dot product function is used to implement the filter. This performs
just one MAC/cycle which is inefficient but was easy to implement as a first
pass. The current Blackfin code also uses an unrolled form of the filter
history to avoid 0 length hardware loop issues. This is wasteful of
memory.
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;
#if defined(__bfin__)
fir->history = kcalloc(2 * taps, sizeof(int16_t), GFP_KERNEL);
#else
fir->history = kcalloc(taps, sizeof(int16_t), GFP_KERNEL);
#endif
return fir->history;
}
static inline void fir16_flush(struct fir16_state_t *fir)
{
#if defined(__bfin__)
memset(fir->history, 0, 2 * fir->taps * sizeof(int16_t));
#else
memset(fir->history, 0, fir->taps * sizeof(int16_t));
#endif
}
static inline void fir16_free(struct fir16_state_t *fir)
{
kfree(fir->history);
}
#ifdef __bfin__
static inline int32_t dot_asm(short *x, short *y, int len)
{
int dot;
len--;
__asm__("I0 = %1;\n\t"
"I1 = %2;\n\t"
"A0 = 0;\n\t"
"R0.L = W[I0++] || R1.L = W[I1++];\n\t"
"LOOP dot%= LC0 = %3;\n\t"
"LOOP_BEGIN dot%=;\n\t"
"A0 += R0.L * R1.L (IS) || R0.L = W[I0++] || R1.L = W[I1++];\n\t"
"LOOP_END dot%=;\n\t"
"A0 += R0.L*R1.L (IS);\n\t"
"R0 = A0;\n\t"
"%0 = R0;\n\t"
: "=&d"(dot)
: "a"(x), "a"(y), "a"(len)
: "I0", "I1", "A1", "A0", "R0", "R1"
);
return dot;
}
#endif
static inline int16_t fir16(struct fir16_state_t *fir, int16_t sample)
{
int32_t y;
#if defined(__bfin__)
fir->history[fir->curr_pos] = sample;
fir->history[fir->curr_pos + fir->taps] = sample;
y = dot_asm((int16_t *) fir->coeffs, &fir->history[fir->curr_pos],
fir->taps);
#else
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];
#endif
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
|
