linux mmap从用户空间应用程序访问PCI内存区域
作者：互联网
作为我的PCI驱动程序的第一级测试,我希望我可以通过/sys/bus/pci/devices/0000:01:00.0/resource0访问pci_iomap区域
来自我的用户应用程序的文mmap的手册页,我找到的示例程序以及其他帖子似乎表明用户进程访问应该有效.但是有些文章似乎表明mmap调用需要通过ioctl访问器在内核中完成.
我的问题是PCI sysfs资源文件的mmap()应该来自应用程序空间吗？
当我运行我的代码时,mmap返回看起来像有效地址的内容但是当我尝试访问虚拟地址时出现Bus错误.
我相信我的终端设备是一个PCI到Xilinx AXI桥接器,它在FPGA上运行正常,因为我可以通过Windows PCIe实用程序(Win驱动程序)进行R / W操作
我使用的是Linux版本3.12.37的NXP LS1021A ARM7处理器.
谢谢
法案
并不是说我希望任何人调试我的代码,但我正在做的事情最好用代码来解释,所以我也把它包括在内.如果粘贴的代码无法正确显示,我深表歉意.希望它能做到.
我运行下面的代码并得到
root @ ls1021aiot：〜#pcimem /sys/bus/pci/devices/0000:01:00.0/resource0 0 w
/sys/bus/pci/devices/0000:01:00.0/resource0已打开.
目标偏移量为0x0,页面大小为4096,映射掩码为0xFFF
mmap(0,4096,0×3,0x1,3,0×0)
mmap(0,4096,0×3,0x1,3,0×0)
PCI内存将4096字节区域映射到map_base 0x76fb5000.
PCI内存映射访问0x 76FB5000.
总线错误
/*
* pcimem.c: Simple program to read/write from/to a pci device from userspace.
*
* Copyright (C) 2010, Bill Farrow (bfarrow@beyondelectronics.us)
*
* Based on the devmem2.c code
* Copyright (C) 2000, Jan-Derk Bakker (J.D.Bakker@its.tudelft.nl)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <signal.h>
#include <fcntl.h>
#include <ctype.h>
#include <termios.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <linux/pci.h>
#define PRINT_ERROR \
do { \
fprintf(stderr, "Error at line %d, file %s (%d) [%s]\n", \
__LINE__, __FILE__, errno, strerror(errno)); exit(1); \
} while(0)
#define MAP_SIZE 4096UL
#define MAP_MASK (MAP_SIZE - 1)
int main(int argc, char **argv) {
int fd;
void *map_base, *virt_addr;
uint32_t read_result, writeval;
char *filename;
off_t target;
int access_type = 'w';
if(argc < 3) {
// pcimem /sys/bus/pci/devices/0001\:00\:07.0/resource0 0x100 w 0x00
// argv[0] [1] [2] [3] [4]
fprintf(stderr, "\nUsage:\t%s { sys file } { offset } [ type [ data ] ]\n"
"\tsys file: sysfs file for the pci resource to act on\n"
"\toffset : offset into pci memory region to act upon\n"
"\ttype : access operation type : [b]yte, [h]alfword, [w]ord\n"
"\tdata : data to be written\n\n",
argv[0]);
exit(1);
}
filename = argv[1];
target = strtoul(argv[2], 0, 0);
if(argc > 3)
access_type = tolower(argv[3][0]);
if((fd = open(filename, O_RDWR | O_SYNC)) == -1){
PRINT_ERROR;
}
printf("%s opened.\n", filename);
printf("Target offset is 0x%x, page size is %ld map mask is 0x%lX\n", (int) target, sysconf(_SC_PAGE_SIZE), MAP_MASK);
fflush(stdout);
/* Map one page */
#if 0
//map_base = mmap(0, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, (off_t) (target & ~MAP_MASK));
//map_base = mmap(0, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, target & ~MAP_MASK);
#endif
printf("mmap(%d, %ld, 0x%x, 0x%x, %d, 0x%x)\n", 0, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, (int) (target & ~MAP_MASK));
map_base = mmap(0, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, (target & ~MAP_MASK));
if(map_base == (void *) -1){
printf("PCI Memory mapped ERROR.\n");
PRINT_ERROR;
close(fd);
return 1;
}
printf("mmap(%d, %ld, 0x%x, 0x%x, %d, 0x%x)\n", 0, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, (int) (target & ~MAP_MASK));
printf("PCI Memory mapped %ld byte region to map_base 0x%08lx.\n", MAP_SIZE, (unsigned long) map_base);
fflush(stdout);
virt_addr = map_base + (target & MAP_MASK);
printf("PCI Memory mapped access 0x %08X.\n", (uint32_t ) virt_addr);
switch(access_type) {
case 'b':
read_result = *((uint8_t *) virt_addr);
break;
case 'h':
read_result = *((uint16_t *) virt_addr);
break;
case 'w':
read_result = *((uint32_t *) virt_addr);
printf("READ Value at offset 0x%X (%p): 0x%X\n", (int) target, virt_addr, read_result);
break;
default:
fprintf(stderr, "Illegal data type '%c'.\n", access_type);
exit(2);
}
fflush(stdout);
if(argc > 4) {
writeval = strtoul(argv[4], 0, 0);
switch(access_type) {
case 'b':
*((uint8_t *) virt_addr) = writeval;
read_result = *((uint8_t *) virt_addr);
break;
case 'h':
*((uint16_t *) virt_addr) = writeval;
read_result = *((uint16_t *) virt_addr);
break;
case 'w':
*((uint32_t *) virt_addr) = writeval;
read_result = *((uint32_t *) virt_addr);
break;
}
printf("Written 0x%X; readback 0x%X\n", writeval, read_result);
fflush(stdout);
}
if(munmap(map_base, MAP_SIZE) == -1) { PRINT_ERROR;}
close(fd);
return 0;
}
解决方法:
您可以查看pci_debug程序代码,可用here.如果您遇到总线错误,则可能是FPGA设计问题.您的IP AXI总线是否接受32位/ 16位/ 8位访问？
确保使用正确的地址访问存储器(如果32位地址必须可被4整除,如果16位乘以2).
标签：linux,pci-e 来源： https://codeday.me/bug/20190608/1198823.html