Linux内核开发-命令行通过MDIO读写PHY寄存器

0. 前言

在进行网络驱动的调试时，可能需要读取MAC寄存器或者PHY寄存器来确认状态是否符合预期。MAC寄存器一般可从厂商获取，PHY寄存器的读写可以通过如下方式进行。

1. PHY寄存器读写

1.1. 源码

#include <stdio.h> 
#include <stdlib.h>
#include <string.h>
#include <linux/mii.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <linux/sockios.h>
#include <linux/types.h>
#include <netinet/in.h>
 
#define ret_check(ret) \
		if(ret < 0){ \
			printf("%m! \"%s\" : line: %d\n", __func__, __LINE__); \
			goto lab; \
		}
 
#define help() \
	printf("read/write phy reg by mdio:\n\n"); \
	printf("commmon reg read operation: \n    sudo ./rw_phy [dev_name] [reg_addr]\n"); \
	printf("commmon reg write operation: \n    sudo ./rw_phy [dev_name] [reg_addr] [value]\n"); \
	printf("\nFor example:\n"); \
	printf("    rw_phy enp1s0 0x0\n"); \
	printf("    rw_phy enp1s0 0x0 0x1234\n\n"); \
	exit(0);
 
int sockfd;
 
int main(int argc, char *argv[]){ 
	if(argc < 3 || !strcmp(argv[1], "-h"))
	{
		help();
	}
	struct mii_ioctl_data *mii = NULL; 
	struct ifreq ifr; 
	int ret; 
	memset(&ifr, 0, sizeof(ifr));
	strncpy(ifr.ifr_name, argv[1], IFNAMSIZ - 1);
	sockfd = socket(PF_LOCAL, SOCK_DGRAM, 0);
	ret_check(sockfd); //get phy address in smi bus 
	ret = ioctl(sockfd, SIOCGMIIPHY, &ifr); 
	ret_check(ret); 
	mii = (struct mii_ioctl_data*)&ifr.ifr_data; 
	if(argc == 3)
	{ 
		mii->reg_num = (uint16_t)strtoul(argv[2], NULL, 0);
		ret = ioctl(sockfd, SIOCGMIIREG, &ifr);
		ret_check(ret);
		printf("read phy addr: 0x%x reg: 0x%x value : 0x%x\n", mii->phy_id, mii->reg_num, mii->val_out);
	}
	else if(argc == 4)
	{ 
		mii->reg_num = (uint16_t)strtoul(argv[2], NULL, 0); 
		mii->val_in = (uint16_t)strtoul(argv[3], NULL, 0); 
		ret = ioctl(sockfd, SIOCSMIIREG, &ifr); 
		ret_check(ret);
		printf("write phy addr: 0x%x reg: 0x%x value : 0x%x\n", mii->phy_id, mii->reg_num, mii->val_in);
	} 
	else
	{
		help();
	}

lab: close(sockfd);
	return 0; 
}

1.2. 使用方式

1. 编译读写寄存器的工具：

gcc phy_read_write.c -o rw_phy

2. 使用方式可参看./rw_phy -h：

user@user-pc:~/$ ./rw_phy -h
read/write phy reg by mdio:

commmon reg read operation: 
    sudo ./rw_phy [dev_name] [reg_addr]
commmon reg write operation: 
    sudo ./rw_phy [dev_name] [reg_addr] [value]

For example:
    rw_phy enp1s0 0x0
    rw_phy enp1s0 0x0 0x1234

4. 读公共寄存器：

sudo ./rw_phy [网络接口名] [目标寄存器号]

5. 写公共寄存器

sudo ./rw_phy [网络接口名] [目标寄存器号] [目标值]

2. 解析

上面的代码中涉及到3个ioctl值：

SIOCGMIIPHY /* 获取PHY地址 */
SIOCGMIIREG /* 读寄存器 */
SIOCSMIIREG /* 写寄存器 */

在执行读写phy寄存器的时候，整体调用路径为：

=>命令行输入
		==>内核dev_eth_ioctl
				==>网卡驱动注册的ioctl回调
						==>通过mdio读写phy

对应源码梳理如下：

1. 通过ioctl之后在内核中的调用如下：

//linux kernel:net/core/dev_ioctl.c
static int dev_ifsioc(struct net *net, struct ifreq *ifr, void __user *data,
		      unsigned int cmd)
{
//省略
	case SIOCGMIIPHY:
	case SIOCGMIIREG:
	case SIOCSMIIREG:
		/* 进每个网络设备注册的ioctl回调 */
		return dev_eth_ioctl(dev, ifr, cmd);
//省略
}

static int dev_eth_ioctl(struct net_device *dev,
			 struct ifreq *ifr, unsigned int cmd)
{
	const struct net_device_ops *ops = dev->netdev_ops;
//省略
	/* 网卡驱动注册的时候的调用 */
	return ops->ndo_eth_ioctl(dev, ifr, cmd);
}

2. 以stmmac为例：

//linux kernel:drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
static const struct net_device_ops stmmac_netdev_ops = {
//省略
	.ndo_eth_ioctl = stmmac_ioctl,
//省略
}

static int stmmac_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
{
//省略
	switch (cmd) {
	case SIOCGMIIPHY:
	case SIOCGMIIREG:
	case SIOCSMIIREG:
		ret = phylink_mii_ioctl(priv->phylink, rq, cmd);
		break;
//省略
}

3. 然后从mii获取信息：

int phylink_mii_ioctl(struct phylink *pl, struct ifreq *ifr, int cmd)
{
//省略
	if (pl->phydev) {
		switch (cmd) {
		case SIOCGMIIPHY:
			mii->phy_id = pl->phydev->mdio.addr;
			fallthrough;

		case SIOCGMIIREG:
			ret = phylink_phy_read(pl, mii->phy_id, mii->reg_num);
			if (ret >= 0) {
				mii->val_out = ret;
				ret = 0;
			}
			break;

		case SIOCSMIIREG:
			ret = phylink_phy_write(pl, mii->phy_id, mii->reg_num,
						mii->val_in);
			break;

		default:
			ret = phy_mii_ioctl(pl->phydev, ifr, cmd);
			break;
		}
	} else //省略

	return ret;
}
EXPORT_SYMBOL_GPL(phylink_mii_ioctl);