1 | /* SPDX-License-Identifier: GPL-2.0-only */ |
2 | /* |
3 | * SpanDSP - a series of DSP components for telephony |
4 | * |
5 | * fir.h - General telephony FIR routines |
6 | * |
7 | * Written by Steve Underwood <steveu@coppice.org> |
8 | * |
9 | * Copyright (C) 2002 Steve Underwood |
10 | * |
11 | * All rights reserved. |
12 | */ |
13 | |
14 | #if !defined(_FIR_H_) |
15 | #define _FIR_H_ |
16 | |
17 | /* |
18 | Ideas for improvement: |
19 | |
20 | 1/ Rewrite filter for dual MAC inner loop. The issue here is handling |
21 | history sample offsets that are 16 bit aligned - the dual MAC needs |
22 | 32 bit aligmnent. There are some good examples in libbfdsp. |
23 | |
24 | 2/ Use the hardware circular buffer facility tohalve memory usage. |
25 | |
26 | 3/ Consider using internal memory. |
27 | |
28 | Using less memory might also improve speed as cache misses will be |
29 | reduced. A drop in MIPs and memory approaching 50% should be |
30 | possible. |
31 | |
32 | The foreground and background filters currenlty use a total of |
33 | about 10 MIPs/ch as measured with speedtest.c on a 256 TAP echo |
34 | can. |
35 | */ |
36 | |
37 | /* |
38 | * 16 bit integer FIR descriptor. This defines the working state for a single |
39 | * instance of an FIR filter using 16 bit integer coefficients. |
40 | */ |
41 | struct fir16_state_t { |
42 | int taps; |
43 | int curr_pos; |
44 | const int16_t *coeffs; |
45 | int16_t *history; |
46 | }; |
47 | |
48 | /* |
49 | * 32 bit integer FIR descriptor. This defines the working state for a single |
50 | * instance of an FIR filter using 32 bit integer coefficients, and filtering |
51 | * 16 bit integer data. |
52 | */ |
53 | struct fir32_state_t { |
54 | int taps; |
55 | int curr_pos; |
56 | const int32_t *coeffs; |
57 | int16_t *history; |
58 | }; |
59 | |
60 | /* |
61 | * Floating point FIR descriptor. This defines the working state for a single |
62 | * instance of an FIR filter using floating point coefficients and data. |
63 | */ |
64 | struct fir_float_state_t { |
65 | int taps; |
66 | int curr_pos; |
67 | const float *coeffs; |
68 | float *history; |
69 | }; |
70 | |
71 | static inline const int16_t *fir16_create(struct fir16_state_t *fir, |
72 | const int16_t *coeffs, int taps) |
73 | { |
74 | fir->taps = taps; |
75 | fir->curr_pos = taps - 1; |
76 | fir->coeffs = coeffs; |
77 | fir->history = kcalloc(n: taps, size: sizeof(int16_t), GFP_KERNEL); |
78 | return fir->history; |
79 | } |
80 | |
81 | static inline void fir16_flush(struct fir16_state_t *fir) |
82 | { |
83 | memset(fir->history, 0, fir->taps * sizeof(int16_t)); |
84 | } |
85 | |
86 | static inline void fir16_free(struct fir16_state_t *fir) |
87 | { |
88 | kfree(objp: fir->history); |
89 | } |
90 | |
91 | static inline int16_t fir16(struct fir16_state_t *fir, int16_t sample) |
92 | { |
93 | int32_t y; |
94 | int i; |
95 | int offset1; |
96 | int offset2; |
97 | |
98 | fir->history[fir->curr_pos] = sample; |
99 | |
100 | offset2 = fir->curr_pos; |
101 | offset1 = fir->taps - offset2; |
102 | y = 0; |
103 | for (i = fir->taps - 1; i >= offset1; i--) |
104 | y += fir->coeffs[i] * fir->history[i - offset1]; |
105 | for (; i >= 0; i--) |
106 | y += fir->coeffs[i] * fir->history[i + offset2]; |
107 | if (fir->curr_pos <= 0) |
108 | fir->curr_pos = fir->taps; |
109 | fir->curr_pos--; |
110 | return (int16_t) (y >> 15); |
111 | } |
112 | |
113 | static inline const int16_t *fir32_create(struct fir32_state_t *fir, |
114 | const int32_t *coeffs, int taps) |
115 | { |
116 | fir->taps = taps; |
117 | fir->curr_pos = taps - 1; |
118 | fir->coeffs = coeffs; |
119 | fir->history = kcalloc(n: taps, size: sizeof(int16_t), GFP_KERNEL); |
120 | return fir->history; |
121 | } |
122 | |
123 | static inline void fir32_flush(struct fir32_state_t *fir) |
124 | { |
125 | memset(fir->history, 0, fir->taps * sizeof(int16_t)); |
126 | } |
127 | |
128 | static inline void fir32_free(struct fir32_state_t *fir) |
129 | { |
130 | kfree(objp: fir->history); |
131 | } |
132 | |
133 | static inline int16_t fir32(struct fir32_state_t *fir, int16_t sample) |
134 | { |
135 | int i; |
136 | int32_t y; |
137 | int offset1; |
138 | int offset2; |
139 | |
140 | fir->history[fir->curr_pos] = sample; |
141 | offset2 = fir->curr_pos; |
142 | offset1 = fir->taps - offset2; |
143 | y = 0; |
144 | for (i = fir->taps - 1; i >= offset1; i--) |
145 | y += fir->coeffs[i] * fir->history[i - offset1]; |
146 | for (; i >= 0; i--) |
147 | y += fir->coeffs[i] * fir->history[i + offset2]; |
148 | if (fir->curr_pos <= 0) |
149 | fir->curr_pos = fir->taps; |
150 | fir->curr_pos--; |
151 | return (int16_t) (y >> 15); |
152 | } |
153 | |
154 | #endif |
155 | |