1、 背景介紹

在zynq中，由于有PL部分的存在，操作系統需要對PL部分的物理地址進行操作，也就是對操作相關IP核的寄存器。除了在驅動中進行映射外（參看前一篇文章點擊打開鏈接），可以直接在用戶態進行地址映射訪問。

2、 IO接口頭文件

如果做過裸奔的應用程序，可以看到用戶app最終調用的接口無非是下面以下這一類函數：

u8 Xil_In8(INTPTR Addr);

u16 Xil_In16(INTPTR Addr);

u32 Xil_In32(INTPTR Addr);

void Xil_Out8(INTPTR Addr, u8 Value);

void Xil_Out16(INTPTR Addr, u16 Value);

void Xil_Out32(INTPTR Addr, u32 Value);

u16 Xil_In16BE(INTPTR Addr);

u32 Xil_In32BE(INTPTR Addr);

void Xil_Out16BE(INTPTR Addr, u16 Value);

void Xil_Out32BE(INTPTR Addr, u32 Value);

在訪問物理地址方面，沒有比這一類函數更底層的了。當在Linux下對這一類函數加以實現，用戶app便可直接訪問PL部分物理地址。實現這一類函數需要進行物理映射，不過由于不是驅動，這種映射可以直接放在應用層實現。

下面是xil_in32()和xil_out32()的具體實現，映射時只需要對/dev/mem映射即可。

#include

#include

#include

#include

#include

#include

#include

#include

#include

#define PAGE_SIZE ((size_t)getpagesize())

#define PAGE_MASK ((uint64_t) (long)~(PAGE_SIZE - 1))

void Xil_Out32(uint64_t phyaddr, uint32_t val)

{

int fd;

volatile uint8_t *map_base;

uint64_t base = phyaddr & PAGE_MASK;

uint64_t pgoffset = phyaddr & (~PAGE_MASK);

if((fd = open("/dev/mem", O_RDWR | O_SYNC)) == -1)

{

perror("open /dev/mem:");

}

map_base = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED,

fd, base);

if(map_base == MAP_FAILED)

{

perror("mmap:");

}

*(volatile uint32_t *)(map_base + pgoffset) = val;

close(fd);

munmap((void *)map_base, PAGE_SIZE);

}

int Xil_In32(uint64_t phyaddr)

{

int fd;

uint32_t val;

volatile uint8_t *map_base;

uint64_t base = phyaddr & PAGE_MASK;

uint64_t pgoffset = phyaddr & (~PAGE_MASK);

//open /dev/mem

if((fd = open("/dev/mem", O_RDWR | O_SYNC)) == -1)

{

perror("open /dev/mem:");

}

//mmap

map_base = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED,

fd, base);

if(map_base == MAP_FAILED)

{

perror("mmap:");

}

val = *(volatile uint32_t *)(map_base + pgoffset);

close(fd);

munmap((void *)map_base, PAGE_SIZE);

return val;

}

3、 應用層實現

應用層中只需要指定起始物理地址，然后調用xil_in32()和xil_out32()進行操作，為了調用方便，可以封裝一層。

#ifndef SMARTCARMOVE_H

#define SMARTCARMOVE_H

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include "move.h"

static int fd;

#define MODE (O_WRONLY | O_TRUNC)

/*

static char *gpio_addr[] = {

"/sys/class/gpio/export",

"/sys/class/gpio/gpio61/direction/","/sys/class/gpio/gpio61/value/",

"/sys/class/gpio/gpio62/direction/","/sys/class/gpio/gpio62/value/",

"/sys/class/gpio/gpio63/direction/","/sys/class/gpio/gpio63/value/",

"/sys/class/gpio/gpio64/direction/","/sys/class/gpio/gpio64/value/"

};

*/

extern void rio_setreg32(unsigned int addrBase,unsigned int addrOffset,unsigned int value);

extern int rio_getreg32(unsigned int addrBase,unsigned int addrOffset);

extern int hlMaintWrite(unsigned int dstId,unsigned short hopcount, unsigned int offset, unsigned int writedata);

extern int hlMaintRead(unsigned int dstId,unsigned short hopcount, unsigned int offset, int mrdataAdr);

#endif

#include "xil_io.h"

#include "move.h"

#define AXI_RIO_BASEADDR 0x40000000

#define AXI_RIO_NODE_BASEADDR 0x10100

#define AXI_RIO_MAX_HOPCOUNT 13

/**

read and write phy mem

* */

void rio_setreg32(unsigned int addrBase,unsigned int addrOffset,unsigned int value)

{

Xil_Out32(addrBase+addrOffset, value);

}

int rio_getreg32(unsigned int addrBase,unsigned int addrOffset)

{

int ans=0;

ans=Xil_In32(addrBase+addrOffset);

return ans;

}

int hlMaintWrite(unsigned int dstId,unsigned short hopcount, unsigned int offset, unsigned int writedata)

{

unsigned int reg_addr;

if( hopcount > AXI_RIO_MAX_HOPCOUNT )

{

printf("!!!error, hopcount = %d, > %d ",hopcount,AXI_RIO_MAX_HOPCOUNT);

return -1;

}

rio_setreg32(AXI_RIO_BASEADDR,AXI_RIO_NODE_BASEADDR,dstId);

reg_addr = (((hopcount+1)<<24)|offset);

rio_setreg32(AXI_RIO_BASEADDR,reg_addr,writedata);

return 0;

}

int hlMaintRead(unsigned int dstId,unsigned short hopcount, unsigned int offset, int mrdataAdr)

{

unsigned int reg_addr;

if( hopcount > AXI_RIO_MAX_HOPCOUNT )

{

printf("!!!error, hopcount = %d, > %d ",hopcount,AXI_RIO_MAX_HOPCOUNT);

return -1;

}

rio_setreg32(AXI_RIO_BASEADDR,AXI_RIO_NODE_BASEADDR,dstId);

reg_addr = (((hopcount+1)<<24)|offset);

mrdataAdr = rio_getreg32(AXI_RIO_BASEADDR,reg_addr);

printf("M_SRIO_MAINT_REG_READ: hopcount = %d, offset = 0x%x, value = 0x%x ",hopcount,offset,mrdataAdr);

return 0;

}

int main(int argc, char *argv[])

{

int mtRdata=0;

printf("get 1848 device id through rio ");

hlMaintRead(0xFF,0, 0, mtRdata);

printf("ok ");

return 0;

}

運行結果如下，可以看到和在驅動中實現一樣

4、 總結

出于安全考慮，在用戶態中直接訪問物理地址，這種做法在linux中不常見，不過對于zynq來說這種方法要比實現驅動后再通過app調用驅動接口間接明了的多。也可以這樣說，是把驅動移植到了用戶態中，在用戶態下實現地址映射。考慮到這一點，上面給出的例子可以作為用戶態中提供給更上一層app的接口，這樣就能避免真正的用戶直接接觸物理地址。