RK3568平台（网络篇）添加网络交换芯片RTL8306M

一.硬件原理图

分析：
该交换芯片支持I2C、SPI、mdio通信，但是看ast1520的uboot代码采用的是mdio去通信phy芯片的，所以暂时也先采用mdio的方式，需要配置相应的引脚才可以配置成mdio通信模式，具体的配置硬件工程师解决。

背景：

RTL8306M芯片上可能没有提供MDC/MDIO接口，可以通过GPIO（General Purpose Input/Output）来模拟，GPIO可实现串行输入输出，且一般CPU上会提供很多GPIO接口供用户自定义使用。每组SMI需要两个GPIO口分别来模拟MDC和MDIO，首先需要保证这两个GPIO口不作其他用途，且相应的复用模式设置为GPIO模式。

二.SMI[MDC/MDIO]协议

SMI：串行管理接口（Serial Management Interface），通常直接被称为MDIO接口（Management Data Input/Output Interface）。MDIO最早在IEEE 802.3的第22卷定义，后来在第45卷又定义了增强版本的MDIO，其主要被应用于以太网的MAC和PHY层之间，用于MAC层器件通过读写寄存器来实现对PHY层器件的操作与管理。

MDIO接口包括两条线，MDIO和MDC，其中MDIO是双向数据线，而MDC是由STA驱动的时钟线。MDC时钟的最高速率一般为2.5MHz，MDC也可以是非固定频率，甚至可以是非周期的。MDIO接口只是会在MDC时钟的上升沿进行采样，而并不在意MDC时钟的频率（类似于I2C接口）。MDIO是一个PHY的管理接口，用来读/写PHY的寄存器，以控制PHY的行为或获取PHY的状态，MDC为MDIO提供时钟。

MAC读取PHY的寄存器:

MAC向PHY的寄存器写入数据:

三.代码实现

原厂提供了芯片RTL8306M的读写逻辑，需要自己实现gpio模拟MDC/MDIO和驱动入口。

Kconfig：

config RTL8309
	tristate "RTL8309 driver"
	default m
	help
		Enable this driver will support network switch control

Makefile：

# SPDX-License-Identifier: GPL-2.0-only
#
# Makefile for the Realtek network device drivers.
#

obj-$(CONFIG_RTL8309)	+= rtl8309.o
rtl8309-objs := rtl8309_main.o mdcmdio.o rtk_api.o rtl8309n_asicdrv.

DTS配置：

rtl_8309: rtl-8309{
		status ="okay";
		compatible = "rtl8309";
        pinctrl-names = "default";
        pinctrl-0 = <&rtl8309_mdio_pin
                 &rtl8309_mdc_pin>;
        rtl8309-mdio-gpios = <&gpio3 RK_PC3 GPIO_ACTIVE_HIGH>;
        rtl8309-mdc-gpios = <&gpio3 RK_PC2 GPIO_ACTIVE_HIGH>;
	};

    rtl-8309 {
        rtl8309_mdio_pin:rtl8309-mdio-gpios{
            rockchip,pins = <3 RK_PC3 RK_FUNC_GPIO &pcfg_pull_up>;
        };
        rtl8309_mdc_pin:rtl8309-mdc-gpios{
            rockchip,pins = <3 RK_PC2 RK_FUNC_GPIO &pcfg_pull_up>;
        };
    };

?实现一个杂散类设备RTL8306M：

#include <linux/miscdevice.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/i2c-dev.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/compat.h>
#include <linux/printk.h>
#include <linux/kobject.h>
#include <linux/version.h>
#include <linux/kthread.h>
#include <linux/gpio.h>
#include <linux/of_gpio.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>

#include "rtk_api.h"
#include "rtl8309_main.h"

#include <linux/delay.h>

#define DRIVER_NAME "RTL8309"

#define RTL8309_DEBUG	1
#if RTL8309_DEBUG
#define DBG(format, args...)					\
	printk(KERN_DEBUG "%s: " format, DRIVER_NAME, ##args)
#define ERR(format, args...)					\
	printk(KERN_ERR "%s: " format, DRIVER_NAME, ##args)
#define WARNING(format, args...)				\
	printk(KERN_WARN "%s: " format, DRIVER_NAME, ##args)
#define INFO(format, args...)					\
	printk(KERN_INFO "%s: " format, DRIVER_NAME, ##args)
#else
#define DBG(format, args...)
#define ERR(format, args...)
#define WARNING(format, args...)
#define INFO(format, args...)
#endif

#define LINK_UP			1		
#define LINK_DOWN		2
#define LINK_UNKNOW		3

int PRE_PORT_STATUS[5]={0,0,0,0,0};

struct rtl8309_dev {
	struct device *dev;
	struct device sys_dev;
	struct gpio_desc *rtl8309_mdio;
	struct gpio_desc *rtl8309_mdc;
    struct delayed_work check_status_work;
	struct mutex status_lock;
	u32 link_status;
};

struct rtl8309_dev *g_rtl8309;
struct rtl8309_dev *rtl8309;

void setGpioDirection(int gpio, uint32_t  dir)
{
	if(gpio == IST_GPIO_RTL8309_MDIO){
		if(dir){
			gpiod_direction_output(g_rtl8309->rtl8309_mdio,1);
		}else{
			gpiod_direction_input(g_rtl8309->rtl8309_mdio);
		}
	}else if(gpio == IST_GPIO_RTL8309_MDC){
		if(dir){
			gpiod_direction_output(g_rtl8309->rtl8309_mdc,1);
		}else{
			gpiod_direction_input(g_rtl8309->rtl8309_mdc);
		}
	}
}

void setGpioOutput(int gpio, uint32_t out )
{
	if(gpio == IST_GPIO_RTL8309_MDIO){
		gpiod_set_value(g_rtl8309->rtl8309_mdio, out);
	}else if(gpio == IST_GPIO_RTL8309_MDC){
		gpiod_set_value(g_rtl8309->rtl8309_mdc, out);
	}
}

void getGpioInput(int gpio,uint32_t *in)
{
	if(gpio == IST_GPIO_RTL8309_MDIO){
		*in = gpiod_get_value(g_rtl8309->rtl8309_mdio);
	}else if(gpio == IST_GPIO_RTL8309_MDC){
		*in = gpiod_get_value(g_rtl8309->rtl8309_mdc);
	}
}

static long rtl8309_ioctl(struct file *file, uint32_t cmd, unsigned long arg)
{
    return 0;
}

static ssize_t rtl8309_write(struct file *file, const char __user *buf,
                 size_t size, loff_t *ppos)
{
    return 1;
}

static ssize_t rtl8309_read(struct file *file, char __user *buf, size_t size,
                loff_t *ppos)
{
    return 1;
}

static void check_link_status(struct work_struct *work)
{
	struct delayed_work *dwork = to_delayed_work(work);
	struct rtl8309_dev *rtl8309 =
		container_of(dwork, struct rtl8309_dev, check_status_work);

	int PORT_ENABLE[5]={0,1,0,1,0};
	int PORT_STATUS[5]={0,0,0,0,0};
	int status = 0;
	int i = 0;
	rtk_port_linkStatus_t pLinkStatus = PORT_LINKDOWN;
	rtk_port_speed_t pSpeed = PORT_SPEED_10M;
	rtk_port_duplex_t pDuplex = PORT_HALF_DUPLEX;

    mutex_lock(&rtl8309->status_lock);
	for(i=0;i<5;i++){
		if(PORT_ENABLE[i] == 1){
			if(rtk_port_phyStatus_get((rtk_port_t)i, &pLinkStatus, &pSpeed, &pDuplex) !=0 ){
				printk("rtk_port_phyStatus_get error:%d",i);
				break;
			}
			printk("GetEthStatus, port= %d, pLinkStatus= %d, pSpeed= %d, pDuplex= %d \n",i, pLinkStatus, pSpeed, pDuplex);
			if(pLinkStatus == PORT_LINKUP){
				PORT_STATUS[i] = 1;
				printk("port_status\n");
				if(PRE_PORT_STATUS[i] != PORT_STATUS[i]){
					printk("port[%d] status changed, set led mode\n",i);
					if(pSpeed == PORT_SPEED_100M){
						printk("port_speed\n");
					}else{
						printk("port_speed error\n");
					}
				}
			}else{
				PORT_STATUS[i] = 0;
				printk("port_status\n");
			}
			PRE_PORT_STATUS[i] = PORT_STATUS[i];
			msleep(10);
		}
	}
	mutex_unlock(&rtl8309->status_lock);
	for(i=0;i<5;i++){
		status = status | PORT_STATUS[i];
	}
	if(status == 0)
		rtl8309->link_status =  LINK_DOWN;
	else if(status == 1)
		rtl8309->link_status =  LINK_UP;
	else 
		rtl8309->link_status =  LINK_UNKNOW;

	schedule_delayed_work(&rtl8309->check_status_work, msecs_to_jiffies(5000));
}

static ssize_t rtl8309_status_read(struct device *dev,
				      struct device_attribute *attr, char *buf)
{
	struct rtl8309_dev *rtl8309 = g_rtl8309;

	printk("rtl8309_status_read rtl8309_status_read:%d\n",rtl8309->link_status);

	return sprintf(buf, "%d\n", rtl8309->link_status);
}

static ssize_t rtl8309_status_write(struct device *dev,
				       struct device_attribute *attr,
				       const char *buf, size_t count)
{
    printk("rtl8309_status_write rtl8309_status_write");

	return count;
}

static DEVICE_ATTR(linkstatus, 0644,
		rtl8309_status_read, rtl8309_status_write);

static const struct file_operations rtl8309_fops = {
    .owner = THIS_MODULE,
    .read = rtl8309_read,
    .write = rtl8309_write,
    .unlocked_ioctl = rtl8309_ioctl,
};

struct miscdevice rtl8309_miscdev = {
    .minor = MISC_DYNAMIC_MINOR,
    .name = "rtl8309_dev",
    .fops = &rtl8309_fops,
};

static int rtl8309_probe(struct platform_device *pdev)
{
    printk("rtl8309_probe");

	struct rtl8309_dev *rtl8309;
	int ret = 0;
	
	rtl8309 = devm_kzalloc(&pdev->dev, sizeof(*rtl8309), GFP_KERNEL);
	if (!rtl8309)
		return -ENOMEM;

	rtl8309->dev = &pdev->dev;

	rtl8309->rtl8309_mdio = devm_gpiod_get_optional(rtl8309->dev,
						     "rtl8309-mdio", GPIOD_OUT_HIGH);
	if (IS_ERR(rtl8309->rtl8309_mdio)) {
		printk("Could not get rtl8367-mdio");
		rtl8309->rtl8309_mdio = NULL;
	}

	rtl8309->rtl8309_mdc = devm_gpiod_get_optional(rtl8309->dev,
						     "rtl8309-mdc", GPIOD_OUT_HIGH);
	if (IS_ERR(rtl8309->rtl8309_mdc)) {
		printk("Could not get rtl8367-mdc ");
		rtl8309->rtl8309_mdc = NULL;
	}

	g_rtl8309 = rtl8309;

    ret = misc_register(&rtl8309_miscdev);
    if (ret) {
        ERR("rtl8309_miscdev ERROR: could not register rtl8309_miscdev device\n");
        return ret;
    }

	ret = device_create_file(rtl8309_miscdev.this_device,
				&dev_attr_linkstatus);
	if (ret) {
		printk("failed to create attr linkstatus");
		return ret;
	}

	mutex_init(&rtl8309->status_lock);

	INIT_DELAYED_WORK(&rtl8309->check_status_work, check_link_status);
	schedule_delayed_work(&rtl8309->check_status_work, msecs_to_jiffies(5000));
		
    return 0;
}

static int rtl8309_remove(struct platform_device *client)
{

    return 0;
}

static const struct of_device_id rtl8309_of_match[] = {
    { .compatible = "rtl8309" },
    {}
};
MODULE_DEVICE_TABLE(of, rtl8309_of_match);

static struct platform_driver rtl8309_driver = {
    .probe = rtl8309_probe,
    .remove = rtl8309_remove,
    .driver = {
        .owner = THIS_MODULE,
        .name = DRIVER_NAME,
        .of_match_table = of_match_ptr(rtl8309_of_match),
    },
};

static int __init rtl8309_init(void)
{
    int ret = platform_driver_register(&rtl8309_driver);
    if (ret != 0) {
        pr_err("Failed to register example driver: %d\n", ret);
        return ret;
    }
    pr_info("Example driver initialized\n");
    return 0;
}

static void __exit rtl8309_exit(void)
{
    platform_driver_unregister(&rtl8309_driver);
    pr_info("Example driver exited\n");
}

module_init(rtl8309_init);
module_exit(rtl8309_exit);


MODULE_DESCRIPTION("rtl8309 GPIO Switch");
MODULE_AUTHOR("Zewei Ye <yezw@ist.com.hk>");
MODULE_LICENSE("GPL v2");

函数说明：rtk_port_phyStatus_get为原厂提供的读取RTL8306M芯片状态的接口，根据返回的状态判断是否有百兆网。