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 SCB (DMA from host)
  30 // to any other SCB. This is useful for AC3 throug SPDIF. SRC (source rate converters)
  31 // task always alters the samples in some how, however it's from 48khz -> 48khz. The
  32 // alterations are not audible, but AC3 wont work.
  33 //
  34 //        ...
  35 //         |
  36 // +---------------+
  37 // | AsynchFGTxSCB |
  38 // +---------------+
  39 //        |
  40 //    subListPtr
  41 //        |
  42 // +--------------+
  43 // |   DMAReader  |
  44 // +--------------+
  45 //        |
  46 //    subListPtr
  47 //        |
  48 // +-------------+
  49 // | PCMReader   |
  50 // +-------------+
  51 // (DMA from host)
  52 //
  53
  54 struct dmaSCB
  55   {
  56     long  dma_reserved1[3];
  57
  58     short dma_reserved2:dma_outBufPtr;
  59
  60     short dma_unused1:dma_unused2;
  61
  62     long  dma_reserved3[4];
  63
  64     short dma_subListPtr:dma_nextSCB;
  65     short dma_SPBptr:dma_entryPoint;
  66
  67     long  dma_strmRsConfig;
  68     long  dma_strmBufPtr;
  69
  70     long  dma_reserved4;
  71
  72     VolumeControl s2m_volume;
  73   };
  74
  75 #export DMAReader
  76 void DMAReader()
  77 {
  78   execChild();
  79   r2 = r0->dma_subListPtr;
  80   r1 = r0->nextSCB;
  81
  82   rsConfig01 = r2->strmRsConfig;
  83   // Load rsConfig for input buffer
  84
  85   rsDMA01 = r2->basicReq.daw,       ,                   tb = Z(0 - rf);
  86   // Load rsDMA in case input buffer is a DMA buffer    Test to see if there is any data to transfer
  87
  88   if (tb) goto execSibling_2ind1 after {
  89       r5 = rf + (-1);
  90       r6 = r1->dma_entryPoint;           // r6 = entry point of sibling task
  91       r1 = r1->dma_SPBptr,               // r1 = pointer to sibling task's SPB
  92           ,   ind = r6;                  // Load entry point of sibling task
  93   }
  94
  95   rsConfig23 = r0->dma_strmRsConfig;
  96   // Load rsConfig for output buffer (never a DMA buffer)
  97
  98   r4 = r0->dma_outBufPtr;
  99
 100   rsa0 = r2->strmBufPtr;
 101   // rsa0 = input buffer pointer
 102
 103   for (i = r5; i >= 0; --i)
 104     after {
 105       rsa2 = r4;
 106       // rsa2 = output buffer pointer
 107
 108       nop;
 109       nop;
 110     }
 111   //*****************************
 112   // TODO: cycles to this point *
 113   //*****************************
 114     {
 115       acc0 =  (rsd0 = *rsa0++1);
 116       // get sample
 117
 118       nop;  // Those "nop"'s are really uggly, but there's
 119       nop;  // something with DSP's pipelines which I don't
 120       nop;  // understand, resulting this code to fail without
 121             // having those "nop"'s (Benny)
 122
 123       rsa0?reqDMA = r2;
 124       // Trigger DMA transfer on input stream,
 125       // if needed to replenish input buffer
 126
 127       nop;
 128       // Yet another magic "nop" to make stuff work
 129
 130       ,,r98 = acc0 $+>> 0;
 131       // store sample in ALU
 132
 133       nop;
 134       // latency on load register.
 135       // (this one is understandable)
 136
 137       *rsa2++1 = r98;
 138       // store sample in output buffer
 139
 140       nop; // The same story
 141       nop; // as above again ...
 142       nop;
 143     }
 144   // TODO: cycles per loop iteration
 145
 146   r2->strmBufPtr = rsa0,,   ;
 147   // Update the modified buffer pointers
 148
 149   r4 = rsa2;
 150   // Load output pointer position into r4
 151
 152   r2 = r0->nextSCB;
 153   // Sibling task
 154
 155   goto execSibling_2ind1 // takes 6 cycles
 156     after {
 157       r98 = r2->thisSPB:entryPoint;
 158       // Load child routine entry and data address
 159
 160       r1 = r9;
 161       // r9 is r2->thisSPB
 162
 163       r0->dma_outBufPtr = r4,,
 164       // Store updated output buffer pointer
 165
 166       ind = r8;
 167       // r8 is r2->entryPoint
 168     }
 169 }