diff options
Diffstat (limited to 'drivers/misc/echo/fir.h')
| -rw-r--r-- | drivers/misc/echo/fir.h | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/drivers/misc/echo/fir.h b/drivers/misc/echo/fir.h new file mode 100644 index 000000000..4d0821025 --- /dev/null +++ b/drivers/misc/echo/fir.h @@ -0,0 +1,154 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * 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. + */ + +#if !defined(_FIR_H_) +#define _FIR_H_ + +/* + 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; + fir->history = kcalloc(taps, sizeof(int16_t), GFP_KERNEL); + return fir->history; +} + +static inline void fir16_flush(struct fir16_state_t *fir) +{ + memset(fir->history, 0, fir->taps * sizeof(int16_t)); +} + +static inline void fir16_free(struct fir16_state_t *fir) +{ + kfree(fir->history); +} + +static inline int16_t fir16(struct fir16_state_t *fir, int16_t sample) +{ + int32_t y; + 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]; + 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 |