1、问题描述
Cross Mapping存在于早期的高通平台中，解决主卡无法注册CDMA问题。最近分析其他问题，发现MTK也支持Cross mapping。TSTS手机插入两张卡，其中一张卡无法注册LTE网络。
2、Log分析
TSTS手机实际上支持双协议栈LTE，第三个协议栈仅仅支持WCDMA，因此如果第三卡注册LTE，需要进行CrossMapping，不然第三卡无法注册。
6313: 07-02 14:12:50.338567 2361 3430 D MTK_SMSVC: [setDefaultDataSubId] num phones=3, subId=1
6314: 07-02 14:12:50.338949 2361 3430 D MTK_SMSVC: [setDefaultDataSubId] phoneId=0 subId=1 RAF=36869
6315: 07-02 14:12:50.339121 2361 3430 D MTK_SMSVC: [setDefaultDataSubId] phoneId=1 subId=2 RAF=32772
6316: 07-02 14:12:50.339195 2361 3430 D MTK_SMSVC: [setDefaultDataSubId] phoneId=2 subId=-1 RAF=32772
11403: 07-02 14:12:55.555335 2361 2361 D ProxyController: setRadioCapability: new request session id=525761425
11404: 07-02 14:12:55.555493 2361 2361 D ProxyController: setRadioCapability: phoneId=0 status=STARTING
11405: 07-02 14:12:55.555617 2361 2361 D ProxyController: setRadioCapability: mOldRadioAccessFamily[0]=36868
11406: 07-02 14:12:55.555672 2361 2361 D ProxyController: setRadioCapability: mNewRadioAccessFamily[0]=36869
11421: 07-02 14:12:55.563736 2361 2361 D ProxyController: setRadioCapability: phoneId=1 status=STARTING
11422: 07-02 14:12:55.563850 2361 2361 D ProxyController: setRadioCapability: mOldRadioAccessFamily[1]=32772
11423: 07-02 14:12:55.563890 2361 2361 D ProxyController: setRadioCapability: mNewRadioAccessFamily[1]=32772
11440: 07-02 14:12:55.571969 2361 2361 D ProxyController: setRadioCapability: phoneId=2 status=STARTING
11441: 07-02 14:12:55.572379 2361 2361 D ProxyController: setRadioCapability: mOldRadioAccessFamily[2]=36869
11442: 07-02 14:12:55.573199 2361 2361 D ProxyController: setRadioCapability: mNewRadioAccessFamily[2]=32772
14267: 07-02 14:12:56.678062 1497 1542 D RtcCapa : 3sim skip switch
14268: 07-02 14:12:56.678077 1497 1542 D RtcCapa : 3sim do switch, new slot:0
14269: 07-02 14:12:56.678090 1497 1542 D RtcCapa : do switch, new slot:0
14358: 07-02 14:12:56.682225 1497 1619 I AT : [2] AT> AT+EFUN=4,3 (RIL_CMD3_RADIO_9 tid:502079839472)
20718: 07-02 14:12:58.796678 1497 1619 I AT : [2] AT> AT+EFUN=0,3 (RIL_CMD3_RADIO_9 tid:502079839472)
27580: 07-02 14:13:00.495329 1497 1570 I AT : [0] AT> AT+EFUN=1 (RIL_CMD_RADIO_9 tid:502818483440)
28287: 07-02 14:13:00.646189 2361 2361 D MtkGsmCdmaPhone: EVENT_UNSOL_RADIO_CAPABILITY_CHANGED: rc: {mPhoneId = 0 mVersion=1 mSession=525761425 mPhase=3 mRadioAccessFamily=36869 mLogicModemId=modem_sys1_ps0 mStatus=1}
28346: 07-02 14:13:00.694625 2361 2361 D MtkGsmCdmaPhone: EVENT_UNSOL_RADIO_CAPABILITY_CHANGED: rc: {mPhoneId = 1 mVersion=1 mSession=525761425 mPhase=3 mRadioAccessFamily=36868 mLogicModemId=modem_sys1_ps1 mStatus=1}
28379: 07-02 14:13:00.716350 2361 2361 D MtkGsmCdmaPhone: EVENT_UNSOL_RADIO_CAPABILITY_CHANGED: rc: {mPhoneId = 2 mVersion=1 mSession=525761425 mPhase=3 mRadioAccessFamily=32772 mLogicModemId=modem_sys1_ps2 mStatus=1}
29267: 07-02 14:13:00.864805 1497 1570 I AT : [0] AT> AT+EFUN=3 (RIL_CMD_RADIO_9 tid:502818483440)
调查RILD发现，当设置DDS后，手机会将最大能力的Capabiltity设置到对应的卡槽上，即mLogicModemId=modem_sys1_ps0为对应的数据卡上
3、解决方案
问题出现时，相关SIM卡对应的Modem没有LTE能力，切换DDS后能正常恢复。