Battery Charging Monitoring

The ACT8945A device driver exposes some charging information in the user space at /sys/devices/platform/ahb/ahb:apb/fc018000.flexcom/fc018600.i2c/i2c-0/0-005b/act8945a-charger/power_supply/act8945a-charger.

Below is the list of all files provided, along with the API documentation quoted from Documentation/ABI/testing/sysfs-class-power and a comment about how it applies to the ACT8945A driver specifically.

• type:

  Describes the main type of the supply. Access: Read Valid values: "Battery", "UPS", "Mains", "USB", "Wireless"

  Supported values:

  • "Battery",

  • "Mains",

  • "USB"

• status:

  Represents the charging status of the battery. Normally this is read-only reporting although for some supplies this can be used to enable/disable charging to the battery. Access: Read, Write Valid values: "Unknown", "Charging", "Discharging", "Not charging", "Full"

  The file is actually read only, the driver not allowing to control the charging phase. Supported values:

  • "Charging"

  • "Full"

  • "Discharging"

  • "Not charging"

• capacity_level:

  Coarse representation of battery capacity. Access: Read Valid values: "Unknown", "Critical", "Low", "Normal", "High", "Full"

  All values are supported by the driver.

• charge_type:

  The file is actually read-only, driver not allowing to change the charging type. Supported values:

  • "N/A",

  • "Fast"

  • "Trickle"

  • "Unknown"

• health:

  Supported values:

  • "Good"

  • "Over voltage"

  • "Safety timer expire"

  • "Overheat"

  • "Unknown"

• current_max:

  In cases of

  • unplugged USB,

  • unplugged battery,

  • both battery and USB plugged, battery fully charged,

  this value is always 0. Otherwise the charging current is given.

• technology:

  Always "Li-ion".

• manufacturer:

  Always "Active-semi".

• model_name:

  Always "ACT8945A"

Example

Real world values of some of the files in 3 different powering scenarios:

Battery Charging Control

Overview

The ACT8945A PMIC provides a couple of charging-related parameters which can be programmed dynamically. However, the device's driver doesn't allow to do this from the userspace. Instead a direct communication through I2C for reading/writing PMIC's registers must be carried out. Conclusive provides a bash script /opt/act8945a-i2c-api.sh simplifying this task. See how to use it in detail with

All charging-related registers can be listed with:

"APCH" stands for "Active Path Charging" and designates a specific registers group (named "output" in ACT8945A's nomenclature).

Of these the TIMRDAT, TEMPDAT, INDAT, CHGDAT, CSTATE, ACINSTAT registers are read-only and describe the powering and charging state, which is sufficiently covered by the built-in driver, and their state is reflected in sysfs.

Registers TIMRSTAT, TEMPSTAT, INSTAT, CHGSTAT, TIMRTOT, TEMPIN, INCON, CHGEOCIN, TIMRPRE, TEMPOUT, INDIS, CHGEOCOUT are all single-bit flags enabling interrupts related to various phases of the charging process. By default all of them are disabled.

The TOTTIMO, PRETIMO, OVPSET registers control some charging parameters:

Finally, SUSCHG is a flag enabling/disabling charging of the battery.

For more details about these registers refer to the ACT8945A's datasheet.

Example: Disabling Charging

Assume the KSTR-SAMA5D27 board is connected to a host through USB and has a semi-discharged battery plugged in. Checking the charging status with

shows that the battery is charging. Reading the SUSCHG ("Suspend Charging") register confirms this

Value 0 means that the charging is not suspended. This can be changed with

The PMIC's state is reflected in sysfs: