| /*************************************************************************** |
| * __________ __ ___. |
| * Open \______ \ ____ ____ | | _\_ |__ _______ ___ |
| * Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ / |
| * Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < < |
| * Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \ |
| * \/ \/ \/ \/ \/ |
| * $Id$ |
| * |
| * Copyright (C) 2006-2007 Thom Johansen |
| * |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU General Public License |
| * as published by the Free Software Foundation; either version 2 |
| * of the License, or (at your option) any later version. |
| * |
| * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY |
| * KIND, either express or implied. |
| * |
| ****************************************************************************/ |
| |
| /* uncomment this to make filtering calculate lower bits after shifting. |
| * without this, "shift" - 1 of the lower bits will be lost here. |
| */ |
| /* #define HIGH_PRECISION */ |
| |
| /* |
| * void eq_filter(int32_t **x, struct eqfilter *f, unsigned num, |
| * unsigned channels, unsigned shift) |
| */ |
| .text |
| .global eq_filter |
| eq_filter: |
| lea.l (-11*4, %sp), %sp |
| movem.l %d2-%d7/%a2-%a6, (%sp) | save clobbered regs |
| move.l (11*4+8, %sp), %a5 | fetch filter structure address |
| move.l (11*4+20, %sp), %d7 | load shift count |
| subq.l #1, %d7 | EMAC gives us one free shift |
| #ifdef HIGH_PRECISION |
| moveq.l #8, %d6 |
| sub.l %d7, %d6 | shift for lower part of accumulator |
| #endif |
| movem.l (%a5), %a0-%a4 | load coefs |
| lea.l (5*4, %a5), %a5 | point to filter history |
| |
| .filterloop: |
| move.l (11*4+4, %sp), %a6 | load input channel pointer |
| addq.l #4, (11*4+4, %sp) | point x to next channel |
| move.l (%a6), %a6 |
| move.l (11*4+12, %sp), %d5 | number of samples |
| movem.l (%a5), %d0-%d3 | load filter history |
| |
| /* d0-d3 = history, d4 = temp, d5 = sample count, d6 = lower shift amount, |
| * d7 = upper shift amount, a0-a4 = coefs, a5 = history pointer, a6 = x[] |
| */ |
| .loop: |
| /* Direct form 1 filtering code. We assume DSP has put EMAC in frac mode. |
| * y[n] = b0*x[i] + b1*x[i - 1] + b2*x[i - 2] + a1*y[i - 1] + a2*y[i - 2], |
| * where y[] is output and x[] is input. This is performed out of order |
| * to do parallel load of input value. |
| */ |
| mac.l %a2, %d1, %acc0 | acc = b2*x[i - 2] |
| move.l %d0, %d1 | fix input history |
| mac.l %a1, %d0, (%a6), %d0, %acc0 | acc += b1*x[i - 1], x[i] -> d0 |
| mac.l %a0, %d0, %acc0 | acc += b0*x[i] |
| mac.l %a3, %d2, %acc0 | acc += a1*y[i - 1] |
| mac.l %a4, %d3, %acc0 | acc += a2*y[i - 2] |
| move.l %d2, %d3 | fix output history |
| #ifdef HIGH_PRECISION |
| move.l %accext01, %d2 | fetch lower part of accumulator |
| move.b %d2, %d4 | clear upper three bytes |
| lsr.l %d6, %d4 | shift lower bits |
| #endif |
| movclr.l %acc0, %d2 | fetch upper part of result |
| asl.l %d7, %d2 | restore fixed point format |
| #ifdef HIGH_PRECISION |
| or.l %d2, %d4 | combine lower and upper parts |
| #endif |
| move.l %d2, (%a6)+ | save result |
| subq.l #1, %d5 | are we done with this channel? |
| jne .loop |
| |
| movem.l %d0-%d3, (%a5) | save history back to struct |
| lea.l (4*4, %a5), %a5 | point to next channel's history |
| subq.l #1, (11*4+16, %sp) | have we processed both channels? |
| jne .filterloop |
| |
| movem.l (%sp), %d2-%d7/%a2-%a6 |
| lea.l (11*4, %sp), %sp |
| rts |
| |