sound/pci/cs46xx/imgs/cwcdma.asp

   1 //
   2 //  Copyright(c) by Benny Sjostrand (benny@hostmobility.com)
   3 //
   4 //  This program is free software; you can redistribute it and/or modify
   5 //  it under the terms of the GNU General Public License as published by
   6 //  the Free Software Foundation; either version 2 of the License, or
   7 //  (at your option) any later version.
   8 //
   9 //  This program is distributed in the hope that it will be useful,
  10 //  but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 //  GNU General Public License for more details.
  13 //
  14 //  You should have received a copy of the GNU General Public License
  15 //  along with this program; if not, write to the Free Software
  16 //  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  17 //
  18
  19
  20 //
  21 // This code runs inside the DSP (cs4610, cs4612, cs4624, or cs4630),
  22 // to compile it you need a tool named SPASM 3.0 and DSP code owned by
  23 // Cirrus Logic(R). The SPASM program will generate a object file (cwcdma.osp),
  24 // the "ospparser"  tool will genereate the cwcdma.h file it's included from
  25 // the cs46xx_lib.c file.
  26 //
  27 //
  28 // The purpose of this code is very simple: make it possible to tranfser
  29 // the samples 'as they are' with no alteration from a PCMreader
  30 // SCB (DMA from host) to any other SCB. This is useful for AC3 through SPDIF.
  31 // SRC (source rate converters) task always alters the samples in somehow,
  32 // however it's from 48khz -> 48khz.
  33 // The alterations are not audible, but AC3 wont work.
  34 //
  35 //        ...
  36 //         |
  37 // +---------------+
  38 // | AsynchFGTxSCB |
  39 // +---------------+
  40 //        |
  41 //    subListPtr
  42 //        |
  43 // +--------------+
  44 // |   DMAReader  |
  45 // +--------------+
  46 //        |
  47 //    subListPtr
  48 //        |
  49 // +-------------+
  50 // | PCMReader   |
  51 // +-------------+
  52 // (DMA from host)
  53 //
  54
  55 struct dmaSCB
  56   {
  57     long  dma_reserved1[3];
  58
  59     short dma_reserved2:dma_outBufPtr;
  60
  61     short dma_unused1:dma_unused2;
  62
  63     long  dma_reserved3[4];
  64
  65     short dma_subListPtr:dma_nextSCB;
  66     short dma_SPBptr:dma_entryPoint;
  67
  68     long  dma_strmRsConfig;
  69     long  dma_strmBufPtr;
  70
  71     long  dma_reserved4;
  72
  73     VolumeControl s2m_volume;
  74   };
  75
  76 #export DMAReader
  77 void DMAReader()
  78 {
  79   execChild();
  80   r2 = r0->dma_subListPtr;
  81   r1 = r0->nextSCB;
  82
  83   rsConfig01 = r2->strmRsConfig;
  84   // Load rsConfig for input buffer
  85
  86   rsDMA01 = r2->basicReq.daw,       ,                   tb = Z(0 - rf);
  87   // Load rsDMA in case input buffer is a DMA buffer    Test to see if there is any data to transfer
  88
  89   if (tb) goto execSibling_2ind1 after {
  90       r5 = rf + (-1);
  91       r6 = r1->dma_entryPoint;           // r6 = entry point of sibling task
  92       r1 = r1->dma_SPBptr,               // r1 = pointer to sibling task's SPB
  93           ,   ind = r6;                  // Load entry point of sibling task
  94   }
  95
  96   rsConfig23 = r0->dma_strmRsConfig;
  97   // Load rsConfig for output buffer (never a DMA buffer)
  98
  99   r4 = r0->dma_outBufPtr;
 100
 101   rsa0 = r2->strmBufPtr;
 102   // rsa0 = input buffer pointer
 103
 104   for (i = r5; i >= 0; --i)
 105     after {
 106       rsa2 = r4;
 107       // rsa2 = output buffer pointer
 108
 109       nop;
 110       nop;
 111     }
 112   //*****************************
 113   // TODO: cycles to this point *
 114   //*****************************
 115     {
 116       acc0 =  (rsd0 = *rsa0++1);
 117       // get sample
 118
 119       nop;  // Those "nop"'s are really uggly, but there's
 120       nop;  // something with DSP's pipelines which I don't
 121       nop;  // understand, resulting this code to fail without
 122             // having those "nop"'s (Benny)
 123
 124       rsa0?reqDMA = r2;
 125       // Trigger DMA transfer on input stream,
 126       // if needed to replenish input buffer
 127
 128       nop;
 129       // Yet another magic "nop" to make stuff work
 130
 131       ,,r98 = acc0 $+>> 0;
 132       // store sample in ALU
 133
 134       nop;
 135       // latency on load register.
 136       // (this one is understandable)
 137
 138       *rsa2++1 = r98;
 139       // store sample in output buffer
 140
 141       nop; // The same story
 142       nop; // as above again ...
 143       nop;
 144     }
 145   // TODO: cycles per loop iteration
 146
 147   r2->strmBufPtr = rsa0,,   ;
 148   // Update the modified buffer pointers
 149
 150   r4 = rsa2;
 151   // Load output pointer position into r4
 152
 153   r2 = r0->nextSCB;
 154   // Sibling task
 155
 156   goto execSibling_2ind1 // takes 6 cycles
 157     after {
 158       r98 = r2->thisSPB:entryPoint;
 159       // Load child routine entry and data address
 160
 161       r1 = r9;
 162       // r9 is r2->thisSPB
 163
 164       r0->dma_outBufPtr = r4,,
 165       // Store updated output buffer pointer
 166
 167       ind = r8;
 168       // r8 is r2->entryPoint
 169     }
 170 }