当初Xilinx技术支持忽悠我用ZYNQ的时候这双核就是其中一条广告词，可回想起来在Standalone下面我还真没好好用过双核所以在这里跟大家分享一下在Standalone下面如何搭建AMP分几个阶段进行，从最简单的做起。

至于什么是AMP和SMP我找了个链接就不做解释了：

多核处理器基础SMP&AMP&BMP - zamely - 博客园

今天要做的事情是先在两个CPU上跑出两个完全并行的程序，相互之间没有交集。然后在把程序下载到Flash中让CPU0唤醒CPU1实现真正的AMP。在这个过程中我们还会分析和解决遇到的问题。

当然做事情之前得查资料，搜索一下文档浏览器以后找到了两篇XAPP1078和XAPP1079：一篇是双裸机，一篇是裸机+Linux。根据需求我选了后者，进去之后就发现自己被坑了。这篇文章是在ISE+XPS的古老环境中实现的，而我自己用的是VIVADO，这就悲剧了！

不过我还是把文档和参考设计down下来了。

在文档中心用AMP做关键字搜到的XAPP1079

接下来是到Xilinx官网下载资料

下载后解压毕竟C代码还是有参考价值的。文档只有32页，跳过ISE和XPS的部分直接看SDK的内容。

看完后我就自己关注的内容总结了一下：

hw_platform不需要对AMP进行设置，主要工作都在SDK上。

需要分别建立两个CPU的APP项目，其中CPU1的向导中要注意处理器选项选择CPU1。

CPU1的BSP SETTING需增加-DUSE_AMP=1。

每个CPU的APP项目的src目录中按照自己预想的存储器分配方案修改lscript.ld文件中的内容，千万注意不要让两个CPU的DDR地址重合，因为你APP的ELF文件是加载到DDR中执行的。由于没有OS，ELF肯定是加载到每个CPU的DDR起始地址。如果有重合那么一个CPU的ELF会覆盖另一个的，别问我是怎么知道的。

我在VIVADO中把开发板上的8位LED灯和七段数码管的24位驱动引脚做到了一个axi_gpio的两个通道上。在两个CPU上分别访问一个通道。

写完两个CPU的APP后，分别debug在各自的CPU上run起来，结果如下图：

然后当我把这个设计固化到flash里后发现只有CPU0跑起来了，为啥啊？这才想起自己down下来的代码，对比代码又查询了UG585才知道原因：即使fsbl已经把CPU1的ELF加载到位，但CPU1是处于waiting状态的。需要CPU发出WFE指令才能唤醒CPU1。而CPU1被唤醒后首先就是从地址0XFFFFFFF0读取地址进行跳转。因此CPU0在发出WFE指令前要在0XFFFFFFF0存入CPU1的DDR起始地址。而0XFFFFFFF0属于OCM的地址范围，所以需要去掉OCM这块儿的Cache属性。下面的代码需要包含库文件"xil_io.h"。

    //Disable cache on OCM
    Xil_SetTlbAttributes(0xFFFF0000,0x14de2);           // S=b1 TEX=b100 AP=b11, Domain=b1111, C=b0, B=b0
    Xil_Out32(CPU1_START_UP_REG, CPU1STARTADR); //CPU1STARTADR=0xFFFFFFF0, CPU1STARTADR=0x20000000);
    dmb(); //waits until write has finished
    print("CPU0: sending the SEV to wake up CPU1\n\r");__asm__("sev");dmb(); //waits until write has finished

修改完成烧写flash成功，运行成功。这是我LED.c的源代码

/***************************** Include Files *********************************/
#include "xparameters.h"
#include "xgpio.h"
#include "xil_printf.h"
#include "xil_io.h"
/************************** Constant Definitions *****************************/
#define LED 0x01   /* Assumes bit 0 of GPIO is connected to an LED  */
/*
 * The following constants map to the XPAR parameters created in the
 * xparameters.h file. They are defined here such that a user can easily
 * change all the needed parameters in one place.
 */
#define GPIO_EXAMPLE_DEVICE_ID  XPAR_GPIO_LEDS_DEVICE_ID

/*
 * The following constant is used to wait after an LED is turned on to make
 * sure that it is visible to the human eye.  This constant might need to be
 * tuned for faster or slower processor speeds.
 */
#define LED_DELAY     10000000

/*
 * The following constant is used to determine which channel of the GPIO is
 * used for the LED if there are 2 channels supported.
 */
#define LED_CHANNEL 2
#define CPU1_START_UP_REG 0xFFFFFFF0
#define CPU1STARTADR 0x20000000
/************************** Variable Definitions *****************************/
/*
 * The following are declared globally so they are zeroed and so they are
 * easily accessible from a debugger
 */
XGpio Gpio; /* The Instance of the GPIO Driver */
/*****************************************************************************/
/**
*
* The purpose of this function is to illustrate how to use the GPIO
* driver to turn on and off an LED.
*
* @param   None
*
* @return  XST_FAILURE to indicate that the GPIO Initialization had
*       failed.
*
* @note        This function will not return if the test is running.
*
******************************************************************************/
int main(void)
{int Status;volatile int Delay;int i;//Disable cache on OCM
    Xil_SetTlbAttributes(0xFFFF0000,0x14de2);           // S=b1 TEX=b100 AP=b11, Domain=b1111, C=b0, B=b0
    Xil_Out32(CPU1_START_UP_REG, CPU1STARTADR); //CPU1STARTADR=0xFFFFFFF0, CPU1STARTADR=0x20000000);
    dmb(); //waits until write has finished
    print("CPU0: sending the SEV to wake up CPU1\n\r");__asm__("sev");dmb(); //waits until write has finished
    xil_printf("Start to light the leds\r\n");/* Initialize the GPIO driver */Status = XGpio_Initialize(&Gpio, GPIO_EXAMPLE_DEVICE_ID);if (Status != XST_SUCCESS) {xil_printf("Gpio Initialization Failed\r\n");return XST_FAILURE;}/* Set the direction for all signals as inputs except the LED output */XGpio_SetDataDirection(&Gpio, LED_CHANNEL, 0);//set all pins as output
    /* Loop forever blinking the LED */while (1){for (i=0;i<8;i++){/* Set one LED light each time */XGpio_DiscreteWrite(&Gpio, LED_CHANNEL, ~(LED<<i));

      <span class="cm">/* Wait a small amount of time so the LED is visible */</span><span class="k">for</span> <span class="p">(</span><span class="n">Delay</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">Delay</span> <span class="o">&lt;</span> <span class="n">LED_DELAY</span><span class="p">;</span> <span class="n">Delay</span><span class="o">++</span><span class="p">);</span><span class="p">}</span>
<span class="p">}</span>
<span class="c1">//xil_printf("Successfully ran Gpio Example\r\n");

/***************************** Include Files /
#include “xparameters.h”
#include “xgpio.h”
#include “xil_printf.h”
/ Constant Definitions /
/
 * The following constants map to the XPAR parameters created in the
 * xparameters.h file. They are defined here such that a user can easily
 * change all the needed parameters in one place.
 /
#define GPIO_EXAMPLE_DEVICE_ID  XPAR_GPIO_LEDS_DEVICE_ID

/
 * The following constant is used to wait after an LED is turned on to make
 * sure that it is visible to the human eye.  This constant might need to be
 * tuned for faster or slower processor speeds.
 /
#define LED_DELAY     100000
/
 * The following constant is used to determine which channel of the GPIO is
 * used for the LED if there are 2 channels supported.
 /
#define LED_CHANNEL 1
const   unsigned   int   Display_Code[10]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F};
const   unsigned   int   Selected_Code[4]={0xEE,0xDD,0xBB,0x77};
/ Function Prototypes /
static int emerge_ledbus(int ledbus0,int ledbus1,int ledsel);
/ Variable Definitions /
/
 * The following are declared globally so they are zeroed and so they are
 * easily accessible from a debugger
 /
XGpio Gpio; / The Instance of the GPIO Driver /
/*************************************/
/

 The purpose of this function is to illustrate how to use the GPIO
 driver to turn on and off an LED.
*
* @param   None
*
* @return  XST_FAILURE to indicate that the GPIO Initialization had
*       failed.
*
* @note        This function will not return if the test is running.
*
*****************************************************************************/
int main(void)
{
int Status;
int led_bus0,led_bus1,led_sel;
volatile int Delay;
int i;
xil_printf(“Start to light the leds\r\n”);
/ Initialize the GPIO driver /
Status = XGpio_Initialize(&Gpio, GPIO_EXAMPLE_DEVICE_ID);
if (Status != XST_SUCCESS) {
xil_printf(“Gpio Initialization Failed\r\n”);
return XST_FAILURE;
}
/ Set the direction for all signals as inputs except the LED output /
XGpio_SetDataDirection(&Gpio, LED_CHANNEL, 0);//set all pins as output
    / Loop forever blinking the LED */
while (1) {

  <span class="k">for</span><span class="p">(</span> <span class="n">i</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span><span class="n">i</span><span class="o">&lt;</span><span class="mi">4</span><span class="p">;</span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="p">{</span><span class="c1">//XGpioPs_Write(&amp;Gpio, LED_BANK, emerge_ledbus(0,0,0xFF));//Close all LEDS