# [Unet] CDMA details

## CDMA vs DMA

### 1. 為何要使用CDMA或是DMA ?
#### Answers:
CDMA和DMA是為了處理CPU掛載的AXI接口內存內部的數據傳輸。

那為何不要直接使用CPU內部的AXI，而要再透過一個CDMA或是DMA? 因為若是想要使用CPU端的DDR的話就必須使用CDMA來操作，最主要使因為ZYNQ並沒有AXI Master的接口，只有Slave (S_AXI_HP0)。


圖1-1.DMA和CDMA的用處


圖1-2.AXI CDMA接口與參數設置。

**S_AXI_LITE連接到ZYNQ，M_AXI連接到BRAM controller，SG不太會使用到所以通常不接，類似下圖。**

圖1-3. CPU與CDMA的接法

**為何不會使用到SG port?**

SG全名為Scatter Gather(分散收集)。
在DMA傳輸數據的過程中，要求source physical address和target physical address要是連續的，但是在某些系統中，例如IA architecture，連續的Memory address在physical addrss不一定會是連續的，所以導致DMA要分成很多次傳輸才能完成。SG port即是將目標地址全部收集起來再一次做傳輸，這樣效率比較高。

### 2. DMA和CDMA之間的差別 ?
#### Answer:
DMA : 

CDMA : 從BRAM到DDR的資料傳輸

### 3. Address editor


### 4. Block Diagram
Pink is BRAM8~15 to AXI_interconnect

Light blue to CPU's S_AXI_HP3

Red to CDMA
Light blue is BRAM0~7 to AXI_interconnect

Deep Green is to CPU

### 5. SDK


#### C code 詳細內容 :
:::spoiler

//#include <stdio.h>
//#include "platform.h"
#include "xil_printf.h"

#include "xparameters.h"
#include "xaxicdma.h"
#include "xil_cache.h"
#include "xil_io.h"

#define PL_BRAM_Addr 0xC0000000
#define PL_BRAM_Addr2 0xC2000000
#define BUFF_LEN  3136  //28*28*4

XAxiCdma_Config *axi_cdma_cfg;
XAxiCdma axi_cdma;


static int SourceAddr  = 0x11000000;
static int DestAddr    = 0x12000000;
static int DestAddr2   = 0x12000070;



int main()
{
//    init_platform();

    print("Initial start......\n\r");



    int Status;

    int *SrcPtr;
    int *DestPtr;

    SrcPtr = (int*)SourceAddr;
    DestPtr = (int*)DestAddr;

    //u32 *rx_buffer = (u32 *) PS_OCM_Addr;
    //u32 *tx_buffer = (u32 *) PL_BRAM_Addr;

    //
    static int Array_0[28][28];
    //static int Array_1[28][28];
    int i,j;
    for (i=0;i<28;i++){
    	for (j=0;j<28;j++){
    		Array_0[i][j] = (i*28+j);
    		//Array_1[i][j] = 0;
    	}
    }

    for (i=0;i<28;i++){
    	for (j=0;j<28;j++){
    		SrcPtr[i*28+j] = Array_0[i][j];
    		DestPtr[i*28+j] = 0;
    	}
    }

    printf("Original SRC_DDR DATA\n\r");
	for(i=0;i<28*1;i++){
		printf("%d  %d at %x\n\r",i,SrcPtr[i],&SrcPtr[i]);
	}
	printf("-------------------------------------------------\n\r");
	printf("Original DEST_DDR DATA\n\r");
	for(i=0;i<28*1;i++){
		printf("%d  %d at %x\n\r",i,DestPtr[i],&DestPtr[i]);
	}
    int *tx_buffer = (int *) SrcPtr;
    int *rx_buffer = (int *) PL_BRAM_Addr;
    int *rx_buffer1 = (int *) PL_BRAM_Addr2;
    u32 *tx_buffer1 = (u32 *) PL_BRAM_Addr;
	u32 *rx_buffer2 = (u32 *) DestAddr;
	u32 *tx_buffer2 = (u32 *) PL_BRAM_Addr2;
	u32 *rx_buffer3 = (u32 *) DestAddr2;


//    printf("%d %d\n\r",SrcPtr[55],2*28);

//    for(i=0;i<28;i++){
//  	  printf("%d  %d at %d\n\r",i,SrcPtr[i],&SrcPtr[i]);
//    }


    // Set up the AXI CDMA
    printf("--Set up the AXI CDMA from DDR to BRAM0\n\r");
    axi_cdma_cfg = XAxiCdma_LookupConfig(XPAR_AXICDMA_0_DEVICE_ID);
    if (!axi_cdma_cfg) {
        printf("AXAxiCdma_LookupConfig failed\n\r");
    }

    Status = XAxiCdma_CfgInitialize(&axi_cdma, axi_cdma_cfg, axi_cdma_cfg->BaseAddress);
    if (Status == XST_SUCCESS ){
        printf("XAxiCdma_CfgInitialize succeed\n\r");
    }
    printf("--Disable Interrupt of AXI CDMA\n\r");
    XAxiCdma_IntrDisable(&axi_cdma, XAXICDMA_XR_IRQ_ALL_MASK);

    if (XAxiCdma_IsBusy(&axi_cdma)) {
    printf("AXI CDMA is busy...\n\r");
    while (XAxiCdma_IsBusy(&axi_cdma));
    }


    Xil_DCacheFlush();
//	printf("%x\n\r", &tx_buffer[0]);
//	printf("%x\n\r", &rx_buffer[0]);
    Status = XAxiCdma_SimpleTransfer(
                                     &axi_cdma,
                                     (u32) tx_buffer,
                                     (u32) rx_buffer,
                                     BUFF_LEN,
                                     NULL,
                                     NULL);
//    printf("%d\n\r",Status);
    Xil_DCacheFlush();
    printf("transaction from DDR to BRAM0 is done\n\r");
    // Set up the AXI CDMA
    for (i=0;i<28;i++){
        	for (j=0;j<28;j++){
        		SrcPtr[i*28+j] = 999;
        	}
        }

//    for(i=0;i<28;i++){
//        printf("%d  %d at %x\n\r",i,SrcPtr[i],&SrcPtr[i]);
//    }


        printf("--Set up the AXI CDMA from DDR to BRAM1\n\r");
        axi_cdma_cfg = XAxiCdma_LookupConfig(XPAR_AXICDMA_0_DEVICE_ID);
        if (!axi_cdma_cfg) {
            printf("AXAxiCdma_LookupConfig failed\n\r");
        }

        Status = XAxiCdma_CfgInitialize(&axi_cdma, axi_cdma_cfg, axi_cdma_cfg->BaseAddress);
        if (Status == XST_SUCCESS ){
            printf("XAxiCdma_CfgInitialize succeed\n\r");
        }
        printf("--Disable Interrupt of AXI CDMA\n\r");
        XAxiCdma_IntrDisable(&axi_cdma, XAXICDMA_XR_IRQ_ALL_MASK);

        if (XAxiCdma_IsBusy(&axi_cdma)) {
        printf("AXI CDMA is busy...\n\r");
        while (XAxiCdma_IsBusy(&axi_cdma));
        }


        Xil_DCacheFlush();
//        printf("%x\n\r", &tx_buffer[0]);
//		printf("%x\n\r", &rx_buffer1[0]);
        Status = XAxiCdma_SimpleTransfer(
                                         &axi_cdma,
                                         (u32) tx_buffer,
                                         (u32) rx_buffer1,
                                         BUFF_LEN,
                                         NULL,
                                         NULL);
//        printf("%d\n\r",Status);
        Xil_DCacheFlush();


    printf("transaction from DDR to BRAM1 is done\n\r");


    // Set up the AXI CDMA
       printf("--Set up the AXI CDMA from BRAM0 to DDR\n\r");
       axi_cdma_cfg = XAxiCdma_LookupConfig(XPAR_AXICDMA_0_DEVICE_ID);
       if (!axi_cdma_cfg) {
           printf("AXAxiCdma_LookupConfig failed\n\r");
       }

       Status = XAxiCdma_CfgInitialize(&axi_cdma, axi_cdma_cfg, axi_cdma_cfg->BaseAddress);
       if (Status == XST_SUCCESS ){
           printf("XAxiCdma_CfgInitialize succeed\n\r");
       }
       printf("--Disable Interrupt of AXI CDMA\n\r");
       XAxiCdma_IntrDisable(&axi_cdma, XAXICDMA_XR_IRQ_ALL_MASK);

       if (XAxiCdma_IsBusy(&axi_cdma)) {
       printf("AXI CDMA is busy...\n\r");
       while (XAxiCdma_IsBusy(&axi_cdma));
       }


       Xil_DCacheFlush();
//       printf("%x\n\r", &tx_buffer1[0]);
//       printf("%x\n\r", &rx_buffer2[0]);
       Status = XAxiCdma_SimpleTransfer(
                                        &axi_cdma,
                                        (u32) tx_buffer1,
                                        (u32) rx_buffer2,
                                        BUFF_LEN/28,
                                        NULL,
                                        NULL);
//       printf("%d\n\r",Status);
       Xil_DCacheFlush();

       printf("transaction from BRAM0 to DDR is done\n\r");

       // Set up the AXI CDMA
              printf("--Set up the AXI CDMA from BRAM1 to DDR\n\r");
              axi_cdma_cfg = XAxiCdma_LookupConfig(XPAR_AXICDMA_0_DEVICE_ID);
              if (!axi_cdma_cfg) {
                  printf("AXAxiCdma_LookupConfig failed\n\r");
              }

              Status = XAxiCdma_CfgInitialize(&axi_cdma, axi_cdma_cfg, axi_cdma_cfg->BaseAddress);
              if (Status == XST_SUCCESS ){
                  printf("XAxiCdma_CfgInitialize succeed\n\r");
              }
              printf("--Disable Interrupt of AXI CDMA\n\r");
              XAxiCdma_IntrDisable(&axi_cdma, XAXICDMA_XR_IRQ_ALL_MASK);

              if (XAxiCdma_IsBusy(&axi_cdma)) {
              printf("AXI CDMA is busy...\n\r");
              while (XAxiCdma_IsBusy(&axi_cdma));
              }


              Xil_DCacheFlush();
//              printf("%x\n\r", &tx_buffer2[0]);
//              printf("%x\n\r", &rx_buffer3[0]);
              Status = XAxiCdma_SimpleTransfer(
                                               &axi_cdma,
                                               (u32) tx_buffer2,
                                               (u32) rx_buffer3,
                                               BUFF_LEN/28,
                                               NULL,
                                               NULL);
//              printf("%d\n\r",Status);
              Xil_DCacheFlush();

              printf("transaction from BRAM1 to DDR is done\n\r");

              for(i=0;i<28*2;i++){
            	if (i == 0){
            		printf("Data transfer from BRAM0 to DEST_DDR[0]~[27]\n\r");
            		printf("Data should be 0~27 :\n\r");
            	}
            	if (i == 28){
            		printf("Data transfer from BRAM1 to DEST_DDR[28]~[55]\n\r");
            		printf("Data should be 999 :\n\r");
            	}
				printf("%d  %d at %x\n\r",i,rx_buffer2[i],&rx_buffer2[i]);
			  }

    //cleanup_platform();
    return 0;
}

:::

### 連結:
圖1-2 : https://www.cnblogs.com/xingce/p/16386108.html

圖1-3 : https://blog.csdn.net/qq_23379273/article/details/102672567

M_AXI_SG : https://blog.csdn.net/baidu_37503452/article/details/79023026

DMA vs CDMA : https://xilinx.eetrend.com/blog/2020/100052890.html

PYNQ 實作 :
https://docs.google.com/document/d/189Y34sIyZ-syknVFp6eB79JaQ1Rmj49x-aGoY_IsBrM/edit?usp=sharing

SmartConnnect and Interconnect :
https://blog.csdn.net/shinn476391300/article/details/102605801

CDMA與DMA詳細比較 :

https://xilinx.eetrend.com/blog/2020/100052890.html

https://xilinx.eetrend.com/blog/2021/100554297.html