Configure battery overcurrent and undervoltage alarms

The Qualcomm PMIC battery current limit (BCL) hardware monitor driver enables real-time detection of battery overcurrent (discharge) and undervoltage conditions. Integrated directly to the Qualcomm PMICs, this driver plays a critical role in safeguarding the battery and overall system by responding to damaging electrical events. The BCL hardware monitors battery voltage and current using dedicated sensing channels with configurable threshold values. It supports multiple alarm levels, each associated with an independent interrupt line. Table: BCL alarm features

Alarms	Threshold levels	Interrupt line
Level 0 (LVL0)	Maximum/Minimum threshold	Mapped to `hwmon min/max`
Level 1 (LVL1)	Critical threshold	Mapped to `hwmon lcrit/crit`

The BCL hardware operates in two distinct modes: Table: BCL modes

BCL modes	Description
BCL in Battery PMIC	Supports both undervoltage and overcurrent monitoring
BCL in Core PMIC	Supports only undervoltage monitoring

`sysfs` attributes

When the driver is loaded, it detects the sensors present on the system and creates corresponding sysfs attributes under /sys/class/hwmon/hwmon<X>/, where <X> is an index assigned based on the presence and order of other hwmon devices in the system.

Battery PMIC attributes

The following attributes are supported for BCL in Battery PMIC (for example, PM7250B): Table: Supported BCL attributes in Battery PMIC

PMIC name	Perm	Description
`curr1_input`	Read-only (RO)	Current in milliamperes (mA)
`curr1_label`	RO	Current sensor label
`curr1_max`	Read/Write (RW)	Level 0 current threshold in mA
`curr1_max_alarm`	RO	Level 0 high current alarm status
`curr1_crit`	RW	Level 1 current threshold in mA
`curr1_crit_alarm`	RO	Level 1 high current alarm status
`in0_input`	RO	Voltage in millivolts (mV)
`in0_label`	RO	Voltage sensor label
`in0_min`	RW	Level 0 low voltage threshold in mV
`in0_min_alarm`	RO	Level 0 low voltage alarm status
`in0_lcrit`	RW	Level 1 low voltage threshold in mV
`in0_lcrit_alarm`	RO	Level 1 low voltage alarm status

Note

Alarm attributes are automatically updated when thresholds are exceeded.

Threshold values can be configured at runtime through the RW attributes.

Following are the examples of sysfs structure for Battery PMIC:

-rw-r--r-- 1 root root 4096 Jan  1 00:05 curr1_crit
-r--r--r-- 1 root root 4096 Jan  1 00:05 curr1_crit_alarm
-r--r--r-- 1 root root 4096 Jan  1 00:05 curr1_input
-r--r--r-- 1 root root 4096 Jan  1 00:05 curr1_label
-rw-r--r-- 1 root root 4096 Jan  1 00:05 curr1_max
-r--r--r-- 1 root root 4096 Jan  1 00:05 curr1_max_alarm
lrwxrwxrwx 1 root root    0 Jan  1 00:05 device -> ../../../c440000.spmi:pmic@8:bcl@1d00
-r--r--r-- 1 root root 4096 Jan  1 00:05 in0_input
-r--r--r-- 1 root root 4096 Jan  1 00:05 in0_label
-rw-r--r-- 1 root root 4096 Jan  1 00:05 in0_lcrit
-r--r--r-- 1 root root 4096 Jan  1 00:05 in0_lcrit_alarm
-rw-r--r-- 1 root root 4096 Jan  1 00:05 in0_min
-r--r--r-- 1 root root 4096 Jan  1 00:05 in0_min_alarm
-r--r--r-- 1 root root 4096 Jan  1 00:05 name

Core PMIC attributes

The following attributes are supported for BCL in Core PMIC (for example, PM8350C): Table: Supported BCL attributes in Core PMIC

PMIC name	Perm	Description
`in0_label`	RO	Voltage sensor label
`in0_min`	RW	Level 0 low voltage threshold in mV
`in0_min_alarm`	RO	Level 0 low voltage alarm status
`in0_lcrit`	RW	Level 1 low voltage threshold in mV
`in0_lcrit_alarm`	RO	Level 1 low voltage alarm status

Note

Alarm attributes are automatically updated when thresholds are exceeded.

Threshold values can be configured at runtime through the RW attributes.

The following are the examples of sysfs structure for Core PMIC:

-r--r--r-- 1 root root 4096 Jan  1 00:03 in0_label
-rw-r--r-- 1 root root 4096 Jan  1 00:03 in0_lcrit
-r--r--r-- 1 root root 4096 Jan  1 00:03 in0_lcrit_alarm
-rw-r--r-- 1 root root 4096 Jan  1 00:03 in0_min
-r--r--r-- 1 root root 4096 Jan  1 00:03 in0_min_alarm
-r--r--r-- 1 root root 4096 Jan  1 00:03 name
lrwxrwxrwx 1 root root    0 Jan  1 00:03 of_node ->

To know more about Qualcomm PMIC BCL, see Patch series of Qualcomm PMIC BCL.

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System

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Battery Current Limiting (BCL)

Configure battery overcurrent and undervoltage alarms

`sysfs` attributes

Battery PMIC attributes

Core PMIC attributes

Next steps

​Configure battery overcurrent and undervoltage alarms

​sysfs attributes

​Battery PMIC attributes

​Core PMIC attributes

​Next steps

Configure battery overcurrent and undervoltage alarms

`sysfs` attributes

Battery PMIC attributes

Core PMIC attributes

Next steps