PHY的12种状态

enum phy_state {
	PHY_DOWN = 0, //关闭网卡
	PHY_STARTING, //PHY设备准备好了，PHY driver尚为准备好
	PHY_READY,       //PHY设备注册成功
	PHY_PENDING,  //PHY芯片挂起
	PHY_UP,              //开启网卡
	PHY_AN,             //网卡自协商
	PHY_RUNNING, //网卡已经插入网线并建立物理连接，该状态可切换到PHY_CHANGELINK
	PHY_NOLINK,    //断网，拔掉网线
	PHY_FORCING,//自动协商失败，强制处理（读phy状态寄存器，设置速率，设置工作模式）
	PHY_CHANGELINK, //LINK检查，当物理连接存在时切换到PHY_RUNING，物理连接不存在时切换到PHY_NOLINK
	PHY_HALTED,   //网卡关闭时，PHY挂起
	PHY_RESUMING //网卡开启时，PHY恢复
};

PHY状态机

PHY指PHY芯片，负责数据传送与接收所需要的电与光信号、线路状态、时钟基准、数据编码和电路等,并向数据链路层设备提供标准接口。
MAC指MAC芯片，属于数据链路层，提供寻址机构、数据帧的构建、数据差错检查、传送控制、向网络层提供标准的数据接口等功能。
PHY_DOWN: phy、phy driver、mac都没准备好

1. 如果phy driver被集成在内核中，PHY.probe后，phydev状态为PHY_READY。
2. 如果phy driver被未集成在内核中，PHY.probe后，phydev状态为PHY_STARTING。

PHY_READY：phy、phy driver已经就绪，mac未准备好
当MAC层加载时，在PHY.start后，phydev状态切换为PHY_UP。

PHY_STARTING：phy准备就绪，phy driver、mac未准备好

1. 当MAC加载时，PHY.start后，phydev状态为PHY_PENDING。
2. 当phy driver加载时，phydev状态为PHY_READY。

PHY_PENDING：phy、mac准备就绪,phy driver未准备好
当phy dirver加载后，phdev状态为PHY_UP

上图中0-->1-->2-->4、0-->2-->4代表phy、phy dirver、mac顺序加载。
0-->1-->3-->4代表phy、mac、phy driver顺序加载。

PHY_UP：phy、phy driver、mac准备就绪
当前状态将启动自动协商，若启动成功则进入PHY_AN，若启动失败则进入PHY_FORCING。

PHY_AN：网卡自协商模式，检测自协商是否完成。
先判断物理链路的状态，如果未LINK则进入PHY_NOLINK，如果LINK则判断自协商是否完成，
自协商完成进入PHY_RUNNING，若自协商超时则重新开启自协商。

PHY_FORCING：强制协商
读link和自协商状态寄存器，如果状态正常则进入PHY_RUNNING模式。

PHY_NOLINK：物理链路未连接
判断物理链路状态，如果LINK，再判断是否支持自协商，若支持待自协商完成后进入PHY_RUNNING模式，
若不支持，直接进入PHY_RUNNING模式。若自协商处于挂起状态，则进入PHY_AN模式。

PHY_RUNNING：正常运行中
获取当前link状态，当link状态发生改变时，进入PHY_CHANGELINK模式。

PHY_CHANGELINK：检查物理链路
物理链路link时，切换到PHY_RUNNING，非LINK时切换到PHY_NOLINK。

PHY_HALTED：网卡关闭phy_stop
挂起phy
PHY_RESUMING: 网卡启用phy_start
恢复phy

phy_state_machine是PHY的状态机函数

/**
 * phy_state_machine - Handle the state machine
 * @work: work_struct that describes the work to be done
 */
void phy_state_machine(struct work_struct *work)
{
	struct delayed_work *dwork = to_delayed_work(work);
	struct phy_device *phydev =
			container_of(dwork, struct phy_device, state_queue);
	bool needs_aneg = false, do_suspend = false;
	enum phy_state old_state;
	int err = 0;
	int old_link;

	mutex_lock(&phydev->lock);

	old_state = phydev->state;

	if (phydev->drv->link_change_notify)
		phydev->drv->link_change_notify(phydev);

	switch (phydev->state) {
	case PHY_DOWN:
	case PHY_STARTING:
	case PHY_READY:
	case PHY_PENDING:
		break;
	case PHY_UP:
		needs_aneg = true;

		phydev->link_timeout = PHY_AN_TIMEOUT;

		break;
	case PHY_AN:
		err = phy_read_status(phydev);
		if (err < 0)
			break;

		/* If the link is down, give up on negotiation for now */
		if (!phydev->link) {
			phydev->state = PHY_NOLINK;
			netif_carrier_off(phydev->attached_dev);
			phydev->adjust_link(phydev->attached_dev);
			break;
		}

		/* Check if negotiation is done.  Break if there's an error */
		err = phy_aneg_done(phydev);
		if (err < 0)
			break;

		/* If AN is done, we're running */
		if (err > 0) {
			phydev->state = PHY_RUNNING;
			netif_carrier_on(phydev->attached_dev);
			phydev->adjust_link(phydev->attached_dev);

		} else if (0 == phydev->link_timeout--)
			needs_aneg = true;
		break;
	case PHY_NOLINK:
		if (phy_interrupt_is_valid(phydev))
			break;

		err = phy_read_status(phydev);
		if (err)
			break;

		if (phydev->link) {
			if (AUTONEG_ENABLE == phydev->autoneg) {
				err = phy_aneg_done(phydev);
				if (err < 0)
					break;

				if (!err) {
					phydev->state = PHY_AN;
					phydev->link_timeout = PHY_AN_TIMEOUT;
					break;
				}
			}
			phydev->state = PHY_RUNNING;
			netif_carrier_on(phydev->attached_dev);
			phydev->adjust_link(phydev->attached_dev);
		}
		break;
	case PHY_FORCING:
		err = genphy_update_link(phydev);
		if (err)
			break;

		if (phydev->link) {
			phydev->state = PHY_RUNNING;
			netif_carrier_on(phydev->attached_dev);
		} else {
			if (0 == phydev->link_timeout--)
				needs_aneg = true;
		}

		phydev->adjust_link(phydev->attached_dev);
		break;
	case PHY_RUNNING:
		/* Only register a CHANGE if we are polling or ignoring
		 * interrupts and link changed since latest checking.
		 */
		if (!phy_interrupt_is_valid(phydev)) {
			old_link = phydev->link;
			err = phy_read_status(phydev);
			if (err)
				break;

			if (old_link != phydev->link)
				phydev->state = PHY_CHANGELINK;
		}
		/*
		 * Failsafe: check that nobody set phydev->link=0 between two
		 * poll cycles, otherwise we won't leave RUNNING state as long
		 * as link remains down.
		 */
		if (!phydev->link && phydev->state == PHY_RUNNING) {
			phydev->state = PHY_CHANGELINK;
			dev_err(&phydev->dev, "no link in PHY_RUNNING\n");
		}
		break;
	case PHY_CHANGELINK:
		err = phy_read_status(phydev);
		if (err)
			break;

		if (phydev->link) {
			phydev->state = PHY_RUNNING;
			netif_carrier_on(phydev->attached_dev);
		} else {
			phydev->state = PHY_NOLINK;
			netif_carrier_off(phydev->attached_dev);
		}

		phydev->adjust_link(phydev->attached_dev);

		if (phy_interrupt_is_valid(phydev))
			err = phy_config_interrupt(phydev,
						   PHY_INTERRUPT_ENABLED);
		break;
	case PHY_HALTED:
		if (phydev->link) {
			phydev->link = 0;
			netif_carrier_off(phydev->attached_dev);
			phydev->adjust_link(phydev->attached_dev);
			do_suspend = true;
		}
		break;
	case PHY_RESUMING:
		if (AUTONEG_ENABLE == phydev->autoneg) {
			err = phy_aneg_done(phydev);
			if (err < 0)
				break;

			/* err > 0 if AN is done.
			 * Otherwise, it's 0, and we're  still waiting for AN
			 */
			if (err > 0) {
				err = phy_read_status(phydev);
				if (err)
					break;

				if (phydev->link) {
					phydev->state = PHY_RUNNING;
					netif_carrier_on(phydev->attached_dev);
				} else	{
					phydev->state = PHY_NOLINK;
				}
				phydev->adjust_link(phydev->attached_dev);
			} else {
				phydev->state = PHY_AN;
				phydev->link_timeout = PHY_AN_TIMEOUT;
			}
		} else {
			err = phy_read_status(phydev);
			if (err)
				break;

			if (phydev->link) {
				phydev->state = PHY_RUNNING;
				netif_carrier_on(phydev->attached_dev);
			} else	{
				phydev->state = PHY_NOLINK;
			}
			phydev->adjust_link(phydev->attached_dev);
		}
		break;
	}

	mutex_unlock(&phydev->lock);

	if (needs_aneg)
		err = phy_start_aneg(phydev);
	else if (do_suspend)
		phy_suspend(phydev);

	if (err < 0)
		phy_error(phydev);

	dev_dbg(&phydev->dev, "PHY state change %s -> %s\n",
		phy_state_to_str(old_state), phy_state_to_str(phydev->state));

	queue_delayed_work(system_power_efficient_wq, &phydev->state_queue,
			   PHY_STATE_TIME * HZ);
}