[Xiaomi Redmi 4a ROMs, Kernels, Recoveries, & Other] changlung:
flash 20201012 rom & twrp, can not turn on wifi. flash back latest stock rom with MiFlash2018-5-28-0.zip solve the problem.

10-14 00:12:29.846 5473 5473 W ueventd : type=1400 audit(0.0:213): avc: denied { search } for name="/" dev="mmcblk0p26" ino=2 scontext=u:r:ueventd:s0 tcontext=u:object_r:persist_file:s0 tclass=dir permissive=0
10-14 00:12:31.302 5455 5455 E Sensors : sns_main.c(447):Timeout waiting for SMGR service. Exit sensors daemon!
10-14 00:12:31.303 5455 5455 W Sensors : sns_main.c(355):sns_main_exit called unlock daemon to exit
10-14 00:12:31.303 5455 5455 E Sensors : sns_main.c(561):Exiting! Err 0
10-14 00:12:31.308 1 1 W libc : Unable to set property "ro.init.updatable_crashing_process_name" to "vendor.sensors.qti": error code: 0xb
10-14 00:12:31.309 1 1 W libc : Unable to set property "ro.init.updatable_crashing" to "1": error code: 0xb
10-14 00:12:31.346 5474 5474 W sensors.qti: type=1400 audit(0.0:214): avc: denied { getattr } for path="/mnt/vendor/persist" dev="mmcblk0p26" ino=2 scontext=u:r:sensors:s0 tcontext=u:object_r:persist_file:s0 tclass=dir permissive=0
10-14 00:12:31.348 5474 5477 E Sensors : sns_fsa_la.c(448):realpath failed for directory name13
10-14 00:12:31.348 5474 5477 E Sensors : sns_fsa_la.c(448):realpath failed for directory name13
10-14 00:12:31.348 5474 5477 E Sensors : sns_fsa_la.c(89):invalid directory path -128
10-14 00:12:31.348 5474 5477 E Sensors : sns_reg_la.c(296):Error creating registry file
10-14 00:12:31.348 5474 5477 W Sensors : sns_reg_mr.c(367):File init failed 5
10-14 00:12:31.346 5474 5474 W sensors.qti: type=1400 audit(0.0:215): avc: denied { getattr } for path="/mnt/vendor/persist" dev="mmcblk0p26" ino=2 scontext=u:r:sensors:s0 tcontext=u:object_r:persist_file:s0 tclass=dir permissive=0
10-14 00:12:41.354 5474 5474 E Sensors : sns_debug_mr.c(366):Sensors DIAG Init: Waiting for diag service timed out
10-14 00:12:41.354 5474 5474 E Sensors : sns_debug_main.c(499):Sensors DIAG init: Can't register with debug
10-14 00:12:41.354 5474 5474 E Sensors : sns_init_la.c(165):Error 5 initializing sns_debug_test_init2
10-14 00:12:43.264 808 1392 E LightsService: Light requested not available on this device. 2
--------- beginning of system
10-14 00:12:43.264 808 1179 V DisplayPowerController: Brightness [25] reason changing to: 'manual', previous reason: 'manual [ dim ]'.
10-14 00:12:43.352 2014 2014 W SettingsMetricsFeature: action(Pair<Integer, Object>... taggedData) is deprecated, Use action(int, int, int, String, int) instead.
10-14 00:12:43.353 808 3408 I WifiService: setWifiEnabled package=com.android.settings uid=1000 enable=true
10-14 00:12:43.354 808 1497 D WifiController: StaEnabledState.enter()
10-14 00:12:43.354 808 1498 D WifiActiveModeWarden: received a message in WifiDisabledState: { when=-1ms what=0 target=com.android.internal.util.StateMachine$SmHandler }
10-14 00:12:43.354 808 1498 D WifiActiveModeWarden: Switching from WifiDisabledState to ClientMode
10-14 00:12:43.354 808 1498 D WifiActiveModeWarden: Entering ClientModeActiveState
10-14 00:12:43.354 808 1498 D WifiClientModeManager: entering IdleState
10-14 00:12:43.354 808 1498 D WifiActiveModeWarden: State changed from client mode. state = 2
10-14 00:12:43.355 808 808 D WifiP2pService: Wifi enabled=false, P2P Interface availability=true
10-14 00:12:43.356 808 1498 I WifiVendorHal: Vendor Hal started successfully
10-14 00:12:43.359 808 1498 I SupplicantStaIfaceHal: Starting supplicant using HIDL
10-14 00:12:43.364 808 1498 I android_os_HwBinder: HwBinder: Starting thread pool for getting: android.hardware.wifi.supplicant@1.0::ISupplicant/default
10-14 00:12:43.365 808 1498 E SupplicantStaIfaceHal: Death handler already present
10-14 00:12:43.368 808 1499 I WifiP2pNative: Registering for interface available listener
10-14 00:12:48.267 808 1179 E LightsService: Light requested not available on this device. 2
10-14 00:12:48.717 1937 1937 D QtiCarrierConfigHelper: WARNING, no carrier configs on phone Id: 0
10-14 00:12:50.845 1937 1937 D QtiCarrierConfigHelper: WARNING, no carrier configs on phone Id: 0
10-14 00:12:51.354 5474 5474 E Sensors : sns_main.c(447):Timeout waiting for SMGR service. Exit sensors daemon!
10-14 00:12:51.355 5474 5474 W Sensors : sns_main.c(355):sns_main_exit called unlock daemon to exit
10-14 00:12:51.355 5474 5474 E Sensors : sns_main.c(561):Exiting! Err 0
10-14 00:12:51.361 1 1 W libc : Unable to set property "ro.init.updatable_crashing_process_name" to "vendor.sensors.qti": error code: 0xb
10-14 00:12:51.362 1 1 W libc : Unable to set property "ro.init.updatable_crashing" to "1": error code: 0xb
10-14 00:12:51.386 5487 5487 W sensors.qti: type=1400 audit(0.0:216): avc: denied { getattr } for path="/mnt/vendor/persist" dev="mmcblk0p26" ino=2 scontext=u:r:sensors:s0 tcontext=u:object_r:persist_file:s0 tclass=dir permissive=0
10-14 00:12:51.395 5487 5490 E Sensors : sns_fsa_la.c(448):realpath failed for directory name13
10-14 00:12:51.396 5487 5490 E Sensors : sns_fsa_la.c(448):realpath failed for directory name13
10-14 00:12:51.386 5487 5487 W sensors.qti: type=1400 audit(0.0:217): avc: denied { getattr } for path="/mnt/vendor/persist" dev="mmcblk0p26" ino=2 scontext=u:r:sensors:s0 tcontext=u:object_r:persist_file:s0 tclass=dir permissive=0
10-14 00:12:51.396 5487 5490 E Sensors : sns_fsa_la.c(89):invalid directory path -128
10-14 00:12:51.396 5487 5490 E Sensors : sns_reg_la.c(296):Error creating registry file
10-14 00:12:51.396 5487 5490 W Sensors : sns_reg_mr.c(367):File init failed 5
10-14 00:12:53.797 479 479 E android.hardware.wifi@1.0-service: Failed to write wlan fw path param: No such device
10-14 00:12:53.797 479 479 E android.hardware.wifi@1.0-service: Failed to change firmware mode
10-14 00:12:53.798 808 1498 D HalDevMgr: updateRttController: no one is interested in RTT controllers
10-14 00:12:53.798 808 1498 E HalDevMgr: executeChipReconfiguration: configureChip error: 9 ()
10-14 00:12:53.798 808 1498 E WifiVendorHal: Failed to create STA iface
10-14 00:12:53.798 808 1498 E WifiNative: Failed to create STA iface in vendor HAL
10-14 00:12:53.798 808 1498 E WifiClientModeManager: Failed to create ClientInterface. Sit in Idle
10-14 00:12:53.798 808 1498 D WifiActiveModeWarden: State changed from client mode. state = 4
10-14 00:12:53.798 808 1498 D WifiClientModeManager: expected stop, not triggering callbacks: newState = 1
10-14 00:12:53.799 808 1498 E WifiNative: Could not get Iface object for interface null
10-14 00:12:53.799 808 1498 D WifiActiveModeWarden: ClientMode failed, return to WifiDisabledState.
10-14 00:12:53.799 808 1498 D WifiController: ClientMode unexpected failure: state unknown
10-14 00:12:53.799 808 1498 D WifiClientModeManager: currentstate: IdleState
10-14 00:12:53.799 808 1498 D WifiScanRequestProxy: Sending scan available broadcast: false
10-14 00:12:53.800 808 808 D WifiP2pService: Wifi enabled=false, P2P Interface availability=true
10-14 00:12:53.802 808 1498 I WifiScanRequestProxy: Scanning is disabled
10-14 00:12:53.805 808 1498 D WifiActiveModeWarden: Entering WifiDisabledState
10-14 00:12:53.805 808 1498 D WifiActiveModeWarden: received a message in WifiDisabledState: { when=-6ms what=3 target=com.android.internal.util.StateMachine$SmHandler }
10-14 00:12:53.805 808 1498 D WifiActiveModeWarden: Switching from WifiDisabledState to WifiDisabled
10-14 00:12:53.805 808 1498 D WifiActiveModeWarden: Entering WifiDisabledState
10-14 00:12:53.807 808 1501 I WifiScanningService: wifi driver unloaded
10-14 00:12:53.808 808 1498 E WifiNative: Could not get Iface object for interface null
10-14 00:13:00.003 1574 1574 D KeyguardClockSwitch: Updating clock: 12:13
10-14 00:13:01.083 1937 1937 D QtiCarrierConfigHelper: WARNING, no carrier configs on phone Id: 0
10-14 00:13:01.399 5487 5487 E Sensors : sns_debug_mr.c(366):Sensors DIAG Init: Waiting for diag service timed out
10-14 00:13:01.400 5487 5487 E Sensors : sns_debug_main.c(499):Sensors DIAG init: Can't register with debug
10-14 00:13:01.400 5487 5487 E Sensors : sns_init_la.c(165):Error 5 initializing sns_debug_test_init2
10-14 00:13:02.457 1915 2387 D QCNEJ/WwanInfoRelay: onServiceStateChanged: dataState: 0 DDS:1 Notify service state update
10-14 00:13:02.458 1937 1937 D ServiceStateProvider: subId=1
10-14 00:13:02.463 2254 2254 D CellBroadcastReceiver: onReceive Intent { act=android.intent.action.SERVICE_STATE flg=0x1000010 cmp=com.android.cellbroadcastreceiver/.CellBroadcastReceiver (has extras) }
10-14 00:13:07.586 1915 2387 D QCNEJ/WwanInfoRelay: onServiceStateChanged: dataState: 0 DDS:1 Notify service state update
10-14 00:13:07.590 1937 1937 D ServiceStateProvider: subId=1
10-14 00:13:07.595 2254 2254 D CellBroadcastReceiver: onReceive Intent { act=android.intent.action.SERVICE_STATE flg=0x1000010 cmp=com.android.cellbroadcastreceiver/.CellBroadcastReceiver (has extras) }
10-14 00:13:10.536 5509 5509 W ueventd : type=1400 audit(0.0:218): avc: denied { search } for name="/" dev="mmcblk0p26" ino=2 scontext=u:r:ueventd:s0 tcontext=u:object_r:persist_file:s0 tclass=dir permissive=0
10-14 00:13:11.401 5487 5487 E Sensors : sns_main.c(447):Timeout waiting for SMGR service. Exit sensors daemon!
10-14 00:13:11.401 5487 5487 W Sensors : sns_main.c(355):sns_main_exit called unlock daemon to exit
10-14 00:13:11.401 5487 5487 E Sensors : sns_main.c(561):Exiting! Err 0
10-14 00:13:11.409 1 1 W libc : Unable to set property "ro.init.updatable_crashing_process_name" to "vendor.sensors.qti": error code: 0xb
10-14 00:13:11.410 1 1 W libc : Unable to set property "ro.init.updatable_crashing" to "1": error code: 0xb
10-14 00:13:11.446 5510 5510 W sensors.qti: type=1400 audit(0.0:219): avc: denied { getattr } for path="/mnt/vendor/persist" dev="mmcblk0p26" ino=2 scontext=u:r:sensors:s0 tcontext=u:object_r:persist_file:s0 tclass=dir permissive=0
10-14 00:13:11.450 5510 5513 E Sensors : sns_fsa_la.c(448):realpath failed for directory name13
10-14 00:13:11.450 5510 5513 E Sensors : sns_fsa_la.c(448):realpath failed for directory name13
10-14 00:13:11.451 5510 5513 E Sensors : sns_fsa_la.c(89):invalid directory path -128
10-14 00:13:11.451 5510 5513 E Sensors : sns_reg_la.c(296):Error creating registry file
10-14 00:13:11.451 5510 5513 W Sensors : sns_reg_mr.c(367):File init failed 5
10-14 00:13:11.446 5510 5510 W sensors.qti: type=1400 audit(0.0:220): avc: denied { getattr } for path="/mnt/vendor/persist" dev="mmcblk0p26" ino=2 scontext=u:r:sensors:s0 tcontext=u:object_r:persist_file:s0 tclass=dir permissive=0