--- /dev/null
+/*
+ * 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
Code Review / kvmfornfv.git / blobdiff