| /*************************************************************************** |
| * __________ __ ___. |
| * 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. |
| * |
| ****************************************************************************/ |
| |
| #include "config.h" |
| |
| /* uncomment this to make filtering calculate lower bits after shifting. |
| * without this, "shift" 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) |
| */ |
| #if CONFIG_CPU == PP5002 |
| .section .icode,"ax",%progbits |
| #else |
| .text |
| #endif |
| .global eq_filter |
| eq_filter: |
| ldr r12, [sp] @ get shift parameter |
| stmdb sp!, { r0-r11, lr } @ save all params and clobbered regs |
| ldmia r1!, { r4-r8 } @ load coefs |
| mov r10, r1 @ loop prelude expects filter struct addr in r10 |
| |
| .filterloop: |
| ldr r9, [sp] @ get pointer to this channels data |
| add r0, r9, #4 |
| str r0, [sp] @ save back pointer to next channels data |
| ldr r9, [r9] @ r9 = x[] |
| ldr r14, [sp, #8] @ r14 = numsamples |
| ldmia r10, { r0-r3 } @ load history, r10 should be filter struct addr |
| str r10, [sp, #4] @ save it for loop end |
| |
| /* r0-r3 = history, r4-r8 = coefs, r9 = x[], r10..r11 = accumulator, |
| * r12 = shift amount, r14 = number of samples. |
| */ |
| .loop: |
| /* Direct form 1 filtering code. |
| * 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 |
| * reuse registers, we're pretty short on regs. |
| */ |
| smull r10, r11, r6, r1 @ acc = b2*x[i - 2] |
| mov r1, r0 @ fix input history |
| smlal r10, r11, r5, r0 @ acc += b1*x[i - 1] |
| ldr r0, [r9] @ load input and fix history in same operation |
| smlal r10, r11, r4, r0 @ acc += b0*x[i] |
| smlal r10, r11, r7, r2 @ acc += a1*y[i - 1] |
| smlal r10, r11, r8, r3 @ acc += a2*y[i - 2] |
| mov r3, r2 @ fix output history |
| mov r2, r11, asl r12 @ get upper part of result and shift left |
| #ifdef HIGH_PRECISION |
| rsb r11, r12, #32 @ get shift amount for lower part |
| orr r2, r2, r10, lsr r11 @ then mix in correctly shifted lower part |
| #endif |
| str r2, [r9], #4 @ save result |
| subs r14, r14, #1 @ are we done with this channel? |
| bne .loop |
| |
| ldr r10, [sp, #4] @ load filter struct pointer |
| stmia r10!, { r0-r3 } @ save back history |
| ldr r11, [sp, #12] @ load number of channels |
| subs r11, r11, #1 @ all channels processed? |
| strne r11, [sp, #12] |
| bne .filterloop |
| |
| add sp, sp, #16 @ compensate for temp storage |
| ldmia sp!, { r4-r11, pc } |
| |