代码路径:/kernel/msm-3.18/drivers/usb/phy/phy_msm_usb.c
msm_otg_probe
（1）工作队列初始化

INIT_WORK(&motg->sm_work, msm_otg_sm_work);
INIT_DELAYED_WORK(&motg->chg_work, msm_chg_detect_work);充电器类型检测的work
INIT_DELAYED_WORK(&motg->id_status_work, msm_id_status_w);batt id状态的work

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（2）注册power supply

motg->usb_psy.name = "usb";//文件节点/sys/class/power_supply/usbmotg->usb_psy.type = POWER_SUPPLY_TYPE_USB;motg->usb_psy.supplied_to = otg_pm_power_supplied_to;motg->usb_psy.num_supplicants = ARRAY_SIZE(otg_pm_power_supplied_to);motg->usb_psy.properties = otg_pm_power_props_usb;//所有支持的propertymotg->usb_psy.num_properties = ARRAY_SIZE(otg_pm_power_props_usb);motg->usb_psy.get_property = otg_power_get_property_usb;motg->usb_psy.set_property = otg_power_set_property_usb;motg->usb_psy.property_is_writeable= otg_power_property_is_writeable_usb;if (!msm_otg_register_power_supply(pdev, motg))psy = &motg->usb_psy;

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下面来重点分析两个工作队列sm_work和chg_detected_work

msm_otg_sm_work
case OTG_STATE_B_IDLE:
switch (motg->chg_state) {case USB_CHG_STATE_UNDEFINED://代码里面定义了USB chg detection涉及的多个状态motg->chg_state = USB_CHG_STATE_IN_PROGRESS;//状态设置为检测中msm_chg_detect_work(&motg->chg_work.work);//启动充电器类型检测的workcase USB_CHG_STATE_DETECTED://充电器类型检测完毕，也就是说上面的chg detect work
完毕后一定会设置该状态。
switch (motg->chg_type) {case USB_DCP_CHARGER:/* fall through */case USB_PROPRIETARY_CHARGER:msm_otg_notify_charger(motg,dcp_max_current);if (!motg->is_ext_chg_dcp)otg->phy->state =OTG_STATE_B_CHARGER;break;case USB_UNSUPPORTED_CHARGER:msm_otg_notify_charger(motg, 0);if (!motg->is_ext_chg_dcp)
otg->phy->state =OTG_STATE_B_CHARGER;break;case USB_CDP_CHARGER:msm_otg_notify_charger(motg,IDEV_CHG_MAX);/* fall through */case USB_SDP_CHARGER:msm_chg_check_dcd_flchg(motg);
msm_otg_start_peripheral(otg, 1);otg->phy->state =OTG_STATE_B_PERIPHERAL;mod_timer(&motg->chg_check_timer,CHG_RECHECK_DELAY);break;

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根据不同的充电器类型都调用了msm_otg_notify_charger函数，该函数一个参数为电流

msm_otg_notify_charger(struct msm_otg *motg, unsigned mA)
dev_dbg(motg->phy.dev, "Requested curr from USB = %u, max-type-c:%u\n",mA, motg->typec_current_max);//打印log信息
/* Save bc1.2 max_curr if type-c charger later moves to diff mode */
->  motg->bc1p2_current_max = mA;
-->if (msm_otg_notify_chg_type(motg))//通知PMIC充电器类型dev_err(motg->phy.dev,"Failed notifying %d charger type to PMIC\n",motg->chg_type);msm_otg_notify_power_supply(motg, mA);//设置其他property属性

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msm_chg_detect_work：
switch (motg->chg_state) {case USB_CHG_STATE_UNDEFINED:case USB_CHG_STATE_IN_PROGRESS:……motg->chg_state = USB_CHG_STATE_WAIT_FOR_DCD;break;case USB_CHG_STATE_WAIT_FOR_DCD:msm_chg_enable_primary_det(motg);motg->chg_state = USB_CHG_STATE_DCD_DONE;
case USB_CHG_STATE_DCD_DONE:vout = msm_chg_check_primary_det(motg);
if (vout && !dm_vlgc) { /* VDAT_REF < DM < VLGC */if (line_state) { /* DP > VLGC */motg->chg_type = USB_PROPRIETARY_CHARGER;//到这里检测出第一种充电器类型proprietary，具体是啥类型也不清楚。motg->chg_state = USB_CHG_STATE_DETECTED;delay = 0;} else {msm_chg_enable_secondary_det(motg);//再做进一步的类型检测motg->chg_state = USB_CHG_STATE_PRIMARY_DONE;}
else { /* DM < VDAT_REF || DM > VLGC */if (line_state) /* DP > VLGC or/and DM > VLGC */motg->chg_type = USB_PROPRIETARY_CHARGER;else if (!dcd) {if (motg->pdata->enable_floated_charger== FLOATING_AS_DCP)motg->chg_type = USB_DCP_CHARGER;//根据配置设置这种情况下的充电器类型到底是DCP还是unsupported的，enable_floated_charger可以在dtsi中配置。else if (motg->pdata->enable_floated_charger== FLOATING_AS_INVALID)motg->chg_type =USB_UNSUPPORTED_CHARGER;} else {motg->chg_type = USB_SDP_CHARGER;//检测到SDP充电器}motg->chg_state = USB_CHG_STATE_DETECTED;//状态设置为检测完成。delay = 0;}
case USB_CHG_STATE_PRIMARY_DONE:vout = msm_chg_check_secondary_det(motg);if (vout)motg->chg_type = USB_DCP_CHARGER;elsemotg->chg_type = USB_CDP_CHARGER;//在secondary检测阶段区分是DCP还是CDPmotg->chg_state = USB_CHG_STATE_SECONDARY_DONE;
case USB_CHG_STATE_SECONDARY_DONE:motg->chg_state = USB_CHG_STATE_DETECTED;// secondary检测完毕整个类型检测完毕，状态设置为detected
case USB_CHG_STATE_DETECTED://下面看检测完毕后又做了哪些工作？看注释！！！
/* Notify the charger type to power supply owner as soon as we determine the charger.*/
msm_otg_notify_chg_type(motg);
queue_work(motg->otg_wq, &motg->sm_work);再次去调度sm_work