06-18-2016, 04:16 PM
(06-18-2016, 03:28 AM)xalius Wrote: I am currently investigating how the battery charger in the PMIC (AXP803) is supported by the software. Being a hardware guy I was working my way up from the bottom side of things, starting with the physical connection and the PMIC:
The battery seems to be connected to the PMIC via a load sensing (current sensing) shunt and the PMIC has a switch that connects the battery to the inputs of the voltage
regulators once certain conditions are met. There is also an input on the battery connector to attach a 10k NTC for monitoring the battery temperature. The PMIC contains a battery charger that charges the battery depending on what DC power source is available (USB/DC IN).
From the AXP803 Datasheet:
- Vbat charge target voltage = 4.2V typical
- Charge current can be set between 200 and 2800mA, 1200mA typical
- Trickle charge current is 10% of normal charge current
- There are two safety timers which can be programmed to limit regular/trickle charging after x minutes (480 min / 50min typical)
- Charging stops in CV mode if the normal charge current drops below 10% of the set charge current
- The NTC monitor has different trip points like cold fault, hot fault for operation and charging which can be programmed in the PMIC
- Battery isolation current is 40uA
- Turning on the PMIC happens by either applying USB/DC_IN or pushing the power button
- Turning off the PMIC happens by undervoltage lockout, fault condition, power button or software writes to a register
- The charger starts working once the voltage input from USB/DC_IN is between 4.1V and 7V
- Input to the regulators is automatically selected from Battery, DC_IN or USB
- USB/DC_IN are preferred over Battery
- If USB and DC_IN are not connected together, DC_IN is preferred over USB
- If USB/DC_IN drops below certain thresholds, Battery takes over
- Input can be controlled by registers
- The function of the charge LED can be controlled via registers
- The PMIC is connected to the A64 via a I2C interface
I have looked at the device tree file and it seems to contain some default setting for the PMIC (and the charger):
Code:pmu0@0 {
compatible = "allwinner,pmu0";
device_type = "pmu0";
pmu_batdeten = <0x00000001>;
pmu_init_chgend_rate = <0x00000014>;
pmu_init_chg_enabled = <0x00000001>;
pmu_init_adc_freq = <0x00000320>;
pmu_init_adcts_freq = <0x00000320>;
pmu_init_chg_pretime = <0x00000046>;
pmu_init_chg_csttime = <0x000002d0>;
pmu_batt_cap_correct = <0x00000001>;
pmu_chg_end_on_en = <0x00000000>;
pmu_pwroff_vol = <0x00000ce4>;
pmu_pwron_vol = <0x00000a28>;
pmu_powkey_off_delay_time = <0x00000000>;
pmu_pwrok_time = <0x00000040>;
pmu_reset_shutdown_en = <0x00000001>;
pmu_restvol_adjust_time = <0x0000003c>;
pmu_ocv_cou_adjust_time = <0x0000003c>;
pmu_vbusen_func = <0x00000001>;
pmu_reset = <0x00000000>;
pmu_IRQ_wakeup = <0x00000001>;
pmu_hot_shutdowm = <0x00000001>;
pmu_inshort = <0x00000000>;
pmu_bat_shutdown_ltf = <0x00000c80>;
pmu_bat_shutdown_htf = <0x000000ed>;
status = "okay";
pmu_id = <0x00000006>;
pmu_twi_addr = <0x00000034>;
pmu_twi_id = <0x00000001>;
pmu_irq_id = <0x00000040>;
pmu_chg_ic_temp = <0x00000000>;
pmu_battery_rdc = <0x00000058>;
pmu_battery_cap = <0x000012c0>;
pmu_runtime_chgcur = <0x000001c2>;
pmu_suspend_chgcur = <0x000005dc>;
pmu_shutdown_chgcur = <0x000005dc>;
pmu_init_chgvol = <0x00001068>;
pmu_ac_vol = <0x00000fa0>;
pmu_ac_cur = <0x00000dac>;
pmu_usbpc_vol = <0x00001130>;
pmu_usbpc_cur = <0x000001f4>;
pmu_battery_warning_level1 = <0x0000000f>;
pmu_battery_warning_level2 = <0x00000000>;
pmu_chgled_func = <0x00000000>;
pmu_chgled_type = <0x00000000>;
pmu_bat_para1 = <0x00000000>;
pmu_bat_para2 = <0x00000000>;
pmu_bat_para3 = <0x00000000>;
pmu_bat_para4 = <0x00000000>;
pmu_bat_para5 = <0x00000000>;
pmu_bat_para6 = <0x00000000>;
pmu_bat_para7 = <0x00000001>;
pmu_bat_para8 = <0x00000001>;
pmu_bat_para9 = <0x00000002>;
pmu_bat_para10 = <0x00000003>;
pmu_bat_para11 = <0x00000004>;
pmu_bat_para12 = <0x0000000a>;
pmu_bat_para13 = <0x00000011>;
pmu_bat_para14 = <0x0000001a>;
pmu_bat_para15 = <0x00000029>;
pmu_bat_para16 = <0x0000002e>;
pmu_bat_para17 = <0x00000033>;
pmu_bat_para18 = <0x00000038>;
pmu_bat_para19 = <0x0000003b>;
pmu_bat_para20 = <0x00000041>;
pmu_bat_para21 = <0x00000045>;
pmu_bat_para22 = <0x0000004b>;
pmu_bat_para23 = <0x0000004f>;
pmu_bat_para24 = <0x00000053>;
pmu_bat_para25 = <0x00000059>;
pmu_bat_para26 = <0x0000005f>;
pmu_bat_para27 = <0x00000062>;
pmu_bat_para28 = <0x00000064>;
pmu_bat_para29 = <0x00000064>;
pmu_bat_para30 = <0x00000064>;
pmu_bat_para31 = <0x00000064>;
pmu_bat_para32 = <0x00000064>;
pmu_bat_temp_enable = <0x00000001>;
pmu_bat_charge_ltf = <0x000008d5>;
pmu_bat_charge_htf = <0x00000184>;
pmu_bat_temp_para1 = <0x00001d2a>;
pmu_bat_temp_para2 = <0x00001180>;
pmu_bat_temp_para3 = <0x00000dbe>;
pmu_bat_temp_para4 = <0x00000ae2>;
pmu_bat_temp_para5 = <0x000008af>;
pmu_bat_temp_para6 = <0x000006fc>;
pmu_bat_temp_para7 = <0x000005a8>;
pmu_bat_temp_para8 = <0x000003c9>;
pmu_bat_temp_para9 = <0x00000298>;
pmu_bat_temp_para10 = <0x000001d2>;
pmu_bat_temp_para11 = <0x00000189>;
pmu_bat_temp_para12 = <0x0000014d>;
pmu_bat_temp_para13 = <0x0000011b>;
pmu_bat_temp_para14 = <0x000000f2>;
pmu_bat_temp_para15 = <0x000000b3>;
pmu_bat_temp_para16 = <0x00000086>;
pmu_powkey_off_time = <0x00001770>;
pmu_powkey_off_func = <0x00000000>;
pmu_powkey_off_en = <0x00000001>;
pmu_powkey_long_time = <0x000005dc>;
pmu_powkey_on_time = <0x000003e8>;
power_start = <0x00000000>;
};
There seems to be a driver for the PMIC in the Linux kernel (drivers/power/axp_power/) that interfaces with the PMIC and is used for register access, controlling the various output voltages (CPU frequency scaling etc...) and the battery charger operation. Some of the information is also exported via sysfs and can be read from /sys/class/power_supply/ , /sys/class/regulator and other places.
My question is now, what would be the correct way to handle battery charging, what would be a good way to set the charger defaults and are there any userspace tools available already that can use the subsystems for monitoring etc... ?
Unless having very good knowledge on Lithium battery charging (I am not), I don't encourage backer to modify the parameter. However, if there is backer has such deep knowledge and interest to do so, that will be awesome. The current charging characteristic gearing toward tablet application which is this SoC original usage.
