AnsweredAssumed Answered

Charger mode on i.MX8MQ and Android 8.1

Question asked by Huanxin Jiang on Jan 29, 2019
Latest reply on Feb 19, 2019 by Huanxin Jiang

We are developing on i.MX8MQ and Android 8.1 BSP. We have battery and need charger manager.


We have implemented the battery/charger drivers and the healthd daemon is working well. Android shows correct battery capacity and charging/discharging information. The question is if we power on the unit by plugging in the USB-C adapter it should boot into “charger” mode that shows a big battery icon on screen and plays charging animation. The method is setting “androidboot.mode=charger” in uboot but when I did this I didn’t see that the “charger” service is running. I can manually start the charger service by the following commands on the console:


$ su

# charger


It then starts the battery animation on the screen that is corresponding to the real battery level, and with the following logs (see attachments):


[   19.315741] charger:

[   19.318054] charger: *************** LAST KMSG ***************

[   19.323904] charger:

[   19.326273] charger: last_kmsg not found. Cold reset?

[   19.331353] charger:

[   19.333634] charger: ************* END LAST KMSG *************

[   19.339481] charger:

[   19.341763] charger: --------------- STARTING CHARGER MODE ---------------

[   19.383070] charger: Could not open animation description at /res/values/charger/animation.txt

[   19.391753] charger: Could not parse animation description. Using default animation.


So the key is to automatically start the “charger” service when “androidboot.mode=charger” is set. I tried to modify device/fsl/evk_8mq/init.rc and system/core/rootdir/init.rc, but it didn’t work. In system/core/init/init.cpp it triggers the “charger” event when boot mode is charger but it looks not working:



Can you help have a look on this?


Attached are a log that including the manual starting of the charger service, and a picture when the charger service is running.


It looks that we just need a simple setting in init.rc that starts the charger service if boot mode is charger. I did the following changes in init.rc, but it doesn’t work:


diff --git a/evk_8mq/init.rc b/evk_8mq/init.rc

index 3309b05..ebbd1a9 100644

--- a/evk_8mq/init.rc

+++ b/evk_8mq/init.rc

@@ -138,6 +138,17 @@ on early-boot

     # Dectect DSF streams when scanning media

     setprop ro.FSL_DSF_PARSER 1


+on charger

+    # Enable Power modes and set the CPU Freq Sampling rates

+    write /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor "powersave"

+    write /sys/devices/system/cpu/cpufreq/ondemand/up_threshold 90

+    write /sys/devices/system/cpu/cpufreq/ondemand/sampling_rate 50000

+    write /sys/devices/system/cpu/cpufreq/ondemand/io_is_busy 1

+    write /sys/devices/system/cpu/cpufreq/ondemand/sampling_down_factor 4

+    write /sys/devices/system/cpu/cpu1/online 0

+    write /sys/devices/system/cpu/cpu2/online 0

+    write /sys/devices/system/cpu/cpu3/online 0


service wpa_supplicant /vendor/bin/hw/wpa_supplicant \

     -ip2p0 -Dnl80211 -c/data/misc/wifi/p2p_supplicant.conf -N \

     -iwlan0 -Dnl80211 -c/data/misc/wifi/wpa_supplicant.conf \

@@ -223,6 +234,9 @@ service g3d /vendor/bin/g3d

     group system



+service charger /sbin/charger

+    class charger


on property:wc_transport.start_hci=true

     start start_hci_filter



Huanxin Jiang