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dm365 dvsdk4里面edma例子的问题

本帖最后由 一只耳朵怪 于 2018-6-22 11:13 编辑

我程序里面需要用到edma，但在看dm365 dvsdk4里面的edma例子时有个地方不明白，请专家指点：
例子是psp里面linuxutil里面的edma例子，edma_test.c里面函数
  1. int edma3_memtomemcpytest_dma(int acnt, int bcnt, int ccnt, int sync_mode,
  2.          int event_queue)
  3. [
  4. int result = 0;
  5. unsigned int dma_ch = 0;
  6. int i;
  7. int count = 0;
  8. unsigned int Istestpassed = 0u;
  9. unsigned int numenabled = 0;
  10. unsigned int BRCnt = 0;
  11. int srcbidx = 0;
  12. int de***idx = 0;
  13. int srccidx = 0;
  14. int descidx = 0;
  15. struct edmacc_param param_set;
  16. /* Initalize source and destination buffers */
  17. for (count = 0u; count < (acnt * bcnt * ccnt); count++) [
  18.   dmabufsrc1[count] = 'A' + (count % 26);
  19.   dmabufdest1[count] = 0;
  20. ]
  21. /* Set B count reload as B count. */
  22. BRCnt = bcnt;
  23. /* Setting up the SRC/DES Index */
  24. srcbidx = acnt;
  25. de***idx = acnt;
  26. /* A Sync Transfer Mode */
  27. srccidx = acnt;
  28. descidx = acnt;
  29. dma_ch = edma_alloc_channel(EDMA_CHANNEL_ANY, callback1, NULL,
  30.    event_queue);

  32. printk("edma3_memtomemcpytest_dma::dma_ch is %dn", dma_ch);
  33. if (dma_ch < 0) [
  34.   DMA_PRINTK
  35.       ("nedma3_memtomemcpytest_dma::edma_alloc_channel failed for dma_ch, error:%dn",
  36.        dma_ch);
  37.   return dma_ch;
  38. ]
  39. edma_set_src(dma_ch, (unsigned long)(dmaphyssrc1), INCR, W8BIT);
  40. edma_set_dest(dma_ch, (unsigned long)(dmaphysdest1), INCR, W8BIT);
  41. edma_set_src_index(dma_ch, srcbidx, srccidx);
  42. edma_set_dest_index(dma_ch, de***idx, descidx);
  43. /*上面输入参数acnt=512，bcnt=8，ccnt=8，我的问题是：
  44. 不明白为什么这里srccidx等于acnt，我查edma_set_src_index的函数解释是
  45. edma_set_src_index - configure DMA source address indexing  
  46. @slot: parameter RAM slot being configured  
  47. @src_bidx: byte offset between source arrays in a frame  
  48. @src_cidx: byte offset between source frames in a block  
  49. src_cidx即块中frame间的字节偏移，我觉得应该是acnt*bcnt才对，怎么会是acnt呢？
  50. 是不是因为下面红字处的edma_start在for循环中要运行bcnt * ccnt次，所以这里每次就传512字节，所以src_cidx和src_cidx都设置成了acnt*/

  52. /* A Sync Transfer Mode */
  53. edma_set_transfer_params(dma_ch, acnt, bcnt, ccnt, BRCnt, ASYNC);
  54. /* Enable the Interrupts on Channel 1 */
  55. edma_read_slot(dma_ch, ¶m_set);
  56. param_set.opt |= (1 << ITCINTEN_SHIFT);
  57. param_set.opt |= (1 << TCINTEN_SHIFT);
  58. param_set.opt |= EDMA_TCC(EDMA_CHAN_SLOT(dma_ch));
  59. edma_write_slot(dma_ch, ¶m_set);
  60. numenabled = bcnt * ccnt;
  61. for (i = 0; i < numenabled; i++) [
  62.   irqraised1 = 0;
  63.   /* Now enable the transfer as many times as calculated above. */
  64.   result = edma_start(dma_ch);
  65.   if (result != 0) [
  66.    DMA_PRINTK
  67.        ("edma3_memtomemcpytest_dma: edma_start failed n");
  68.    break;
  69.   ]
  70.   /* Wait for the Completion ISR. */
  71.   while (irqraised1 == 0u) ;
  72.   /* Check the status of the completed transfer */
  73.   if (irqraised1 < 0) [
  74.    /* Some error occured, break from the FOR loop. */
  75.    DMA_PRINTK("edma3_memtomemcpytest_dma: "
  76.        "Event Miss Occured!!!n");
  77.    break;
  78.   ]
  79. ]
  80. if (0 == result) [
  81.   for (i = 0; i < (acnt * bcnt * ccnt); i++) [
  82.    if (dmabufsrc1 != dmabufdest1) [
  83.     DMA_PRINTK
  84.         ("n edma3_memtomemcpytest_dma: Data write-read matching failed at = %un",
  85.          i);
  86.     Istestpassed = 0u;
  87.     result = -1;
  88.     break;
  89.    ]
  90.   ]
  91.   if (i == (acnt * bcnt * ccnt)) [
  92.    Istestpassed = 1u;
  93.   ]
  94.   edma_stop(dma_ch);
  95.   edma_clean_channel(dma_ch);
  96.   edma_free_slot(dma_ch);
  97.   edma_free_channel(dma_ch);
  98. ]
  99. if (Istestpassed == 1u) [
  100.   DMA_PRINTK
  101.       ("nedma3_memtomemcpytest_dma: EDMA Data Transfer Successfull n");
  102. ] else [
  103.   DMA_PRINTK
  104.       ("nedma3_memtomemcpytest_dma: EDMA Data Transfer Failed n");
  105. ]
  106. return result;
  107. ]

谢谢专家！期待您的指导！

回帖（1）

殷晓婷

2018-6-22 03:19:30
参见 DM365 data sheet, Chapter "EDMA" section "Functional Description", "Types of EDMA3 transfers",  "A synchronized transfer", 由图可见在A-synchronous transfer中，为了实现frame 的连续传输需要使 cidx = bidx.
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