USB port 如何识别不同的Charger类型

基于Qualcom 8960/8921平台

一，软件分析

1.  USB charger types & Power supply types

USB_INVALID_CHARGER              Invalid USB charger.

USB_SDP_CHARGER                       Standard downstream port. Refers to a downstream port  on USB2.0 compliant host/hub.

USB_DCP_CHARGER                      Dedicated charger port (AC charger/ Wall charger).

USB_CDP_CHARGER                      Charging downstream port. Enumeration can happen and IDEV_CHG_MAX can be drawn irrespective of USB state.

USB_ACA_A_CHARGER                                B-device is connected on accessory port with charger connected on charging port. This configuration allows charging in host mode.

USB_ACA_B_CHARGER                 No device (or A-device without VBUS) is connected on accessory port with charger connected on charging port.

USB_ACA_C_CHARGER                 A-device (with VBUS) is connected on accessory port with charger connected on charging port.

USB_ACA_DOCK_CHARGER        A docking station that has one upstream port and one or more downstream ports. Capable of supplying IDEV_CHG_MAX irrespective of devices connected on 
accessory ports.

USB_PROPRIETARY_CHARGER   A proprietary charger pull DP and DM to specific voltages between 2.0-3.3v for identification.

POWER_SUPPLY_TYPE_USB,                      /* Standard Downstream Port */

POWER_SUPPLY_TYPE_USB_DCP,           /* Dedicated Charging Port */

POWER_SUPPLY_TYPE_USB_CDP,           /* Charging Downstream Port */

POWER_SUPPLY_TYPE_USB_ACA,           /* Accessory Charger Adapters */

POWER_SUPPLY_TYPE_BMS,                     /* Battery Monitor System */

2. How to classify or identify charger?

USB_SDP_CHARGER	POWER_SUPPLY_TYPE_USB	USB Charger
USB_CDP_CHARGER	POWER_SUPPLY_TYPE_USB_CDP
USB_ACA_DOCK_CHARGER	POWER_SUPPLY_TYPE_USB_ACA
USB_ACA_A_CHARGER
USB_ACA_B_CHARGER
USB_ACA_C_CHARGER
USB_DCP_CHARGER	POWER_SUPPLY_TYPE_USB_DCP	AC Charger
USB_PROPRIETARY_CHARGER

As for the DMS, refer to bold font items, so it is USB charger.

3. Analysis about source codes

*******************************************************************

###用户空间的分析如下：

1. 检查 /sys/class/power_supply/pm8921-dc/online和 /sys/class/power_supply/usb/online 的值,可以知道是何充电器类型

@frameworks/base/services/jni/com_android_server_batteryservice.cpp中有

int register_android_server_BatteryService(JNIEnv* env)

｛

if (strcmp(buf, "Mains") == 0) { ///sys/class/power_supply/pm8921-dc/type == Mains

snprintf(path, sizeof(path), "%s/%s/online", POWER_SUPPLY_PATH, name);

if (access(path, R_OK) == 0)

gPaths.acOnlinePath = strdup(path);

}

｝

如果/sys/class/power_supply/pm8921-dc/online==1,则插入的充电器是wall
charger

      /sys/class/power_supply/usb/online==1, 则插入的充电器是usb charger

调试路径：/sys/kernel/debug/msm_otg

2. 分析frameworks/base/services/jni/com_android_server_batteryservice.cpp

a.函数register_android_server_BatteryService将为被frameworks/base/services/jni/onload.cpp中的JNI_OnLoad调用，用于关联java和C++之间的变量

b.jclass clazz = env->FindClass("com/android/server/BatteryService"); //根据java的路径找到batteryservice.java对应的jclass

gFieldIds.mAcOnline = env->GetFieldID(clazz, "mAcOnline", "Z");

gFieldIds.mUsbOnline = env->GetFieldID(clazz, "mUsbOnline", "Z"); //用于关联batteryservice.java中变量private
boolean mAcOnline和gFieldIds.mAcOnline

c. android_server_BatteryService_update

static JNINativeMethod sMethods[] = {

/* name, signature, funcPtr */

{"native_update", "()V", (void*)android_server_BatteryService_update},

};

关联到native_update@frameworks/base/services/java/com/android/server/batteryservice.java

3. 分析frameworks/base/services/java/com/android/server/batteryservice.java

a. mPowerSupplyObserver.startObserving("SUBSYSTEM=power_supply"); //注册监听该uevent

b.     private UEventObserver mPowerSupplyObserver = new UEventObserver() {

public void onUEvent(UEventObserver.UEvent event) { //如果就收到来自kernel的uevent,触发该函数

update(); //-->native_update();和processValues();

}

};

c. native_update函数会通过JNI调用得到更新的mAcOnline和mUsbOnline值

d. processValues会根据mAcOnline和mUsbOnline值对mPlugType赋值

if (mAcOnline) {

mPlugType = BatteryManager.BATTERY_PLUGGED_AC;

} else if (mUsbOnline) {

mPlugType = BatteryManager.BATTERY_PLUGGED_USB;

} else {

mPlugType = BATTERY_PLUGGED_NONE;

}

e. sendIntent函数会准备Intent并且broadcast这个Intent

Intent intent = new Intent(Intent.ACTION_BATTERY_CHANGED); //public static final String ACTION_BATTERY_CHANGED = "android.intent.action.BATTERY_CHANGED";@batteryservice.java

intent.addFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY

| Intent.FLAG_RECEIVER_REPLACE_PENDING);

intent.putExtra(BatteryManager.EXTRA_PLUGGED, mPlugType);

ActivityManagerNative.broadcastStickyIntent(intent, null);

4. 分析vendor/semc/packages/apps/debugmenu/src/com/sonyericsson/debugmenu/battery.java

a. 接收intent

private BroadcastReceiver mBatteryInfoReceiver = new BroadcastReceiver() {

@Override

public void onReceive(Context arg0, Intent intent) {

if (intent.getAction().equals(Intent.ACTION_BATTERY_CHANGED)) {

mPowerInformation.parseIntent(intent);

updateViews();

}

}

};

public void registerBroadcastReceivers() {

IntentFilter mIntentFilter;

mIntentFilter = new IntentFilter();

mIntentFilter.addAction(Intent.ACTION_BATTERY_CHANGED); //只接收Intent.ACTION_BATTERY_CHANGED的intent

// Register battery receiver.

registerReceiver(mBatteryInfoReceiver, mIntentFilter);

}

b. parseIntent 得到最新的"plugged"值赋给mPlugged

c. updateViews 更新charger类型显示

###内核空间

1. 插入充电器触发的过程@kernel/drivers/usb/otg/msm_otg.c

a. CONFIG_PM_RUNTIME 定义 @kernel/arch/arm/configs/viskan_huashan_defconfig

b.msm_otg_runtime_resume-->msm_otg_resume-->??-->msm_otg_sm_work

c.msm_otg_sm_work,先进入OTG_STATE_UNDEFINED case，然后进入OTG_STATE_B_IDLE
case-->motg->chg_state=USB_CHG_STATE_UNDEFINED-->启动msm_chg_detect_work

d.msm_chg_detect_work 该函数主要完成USB charger类型的识别

USB_CHG_STATE_UNDEFINED //其中psy = power_supply_get_by_name("usb");很关键，表明只是获取usb的power_supply,实际上就是chip->usb_psy@pm8921-charger.c

USB_CHG_STATE_WAIT_FOR_DCD         //Waiting for Data pins contact.

然后多次(MSM_CHG_DCD_MAX_RETRIES=6)检测USB状态，启动queue_delayed_work(motg->wq,
&motg->chg_work, delay); //motg->chg_work=msm_chg_detect_work

USB_CHG_STATE_DETECTED //最后USB charge类型检测完毕

e. 启动queue_work(motg->wq, &motg->sm_work); //motg->sm_work=msm_otg_sm_work

f. 由于motg->chg_state==USB_CHG_STATE_DETECTED,

motg->chg_type==USB_DCP_CHARGER -->msm_otg_notify_charger(motg,IDEV_CHG_MAX);//IDEV_CHG_MAX=1500

2. 发送uevent到用户层

a. msm_otg_notify_charger@kernel/drivers/usb/otg/msm_otg.c

b. -->msm_otg_notify_chg_type@msm_otg.c,该函数中充电类型只归纳成4种：POWER_SUPPLY_TYPE_USB,POWER_SUPPLY_TYPE_USB_CDP,POWER_SUPPLY_TYPE_USB_DCP,POWER_SUPPLY_TYPE_USB_ACA,POWER_SUPPLY_TYPE_BATTERY

c. -->power_supply_set_supply_type@power_supply_core.c // set type of
the power supply

d. -->psy->set_property(psy, POWER_SUPPLY_PROP_TYPE,&ret);

那么在用usb_psy.get_property和dc_psy.get_property
(在函数中pm8921_charger_probe)读取property时

如果是USB type,则在pm_power_get_property_usb读取POWER_SUPPLY_PROP_ONLINE的值,其中POWER_SUPPLY_TYPE_USB，POWER_SUPPLY_TYPE_USB_CDP和POWER_SUPPLY_TYPE_USB_ACA都被归纳成USB
charger

如果是AC type,则在pm_power_get_property_mains读取POWER_SUPPLY_PROP_ONLINE的值，只有POWER_SUPPLY_TYPE_USB_DCP为AC
charger.

e. psy=chip->usb_psy@pm8921-charger.c,所以继续调用的是pm_power_set_property_usb@pm8921-charger.c

f. -->pm8921_set_usb_power_supply_type(val->intval)@pm8921-charger.c

-->power_supply_changed(&the_chip->usb_psy);

-->power_supply_changed(&the_chip->dc_psy);

g. power_supply_changed@pm8921-charger.c , 就会马上发送uevent给user
space,然后user space通过sysfs得到USB
type变化后的信息，参考用户空间的分析

二、硬件分析

主要是通过特殊设计的电路，检测不同的pin的状态，从而确定是何种类型的Charger. 更details的内容省略。