power: supply: Add support for Maxim MAX8971 charger

The MAX8971 is a compact, high-frequency, high-efficiency switch-mode
charger for a one-cell lithium-ion (Li+) battery.

Signed-off-by: Svyatoslav Ryhel <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sebastian Reichel <[email protected]>

Author: clamor-s

Documentation/ABI/testing/sysfs-class-power

@@ -822,3 +822,46 @@ Description:
 		Each entry is a link to the device which registered the extension.
 
 		Access: Read
+
+What:		/sys/class/power_supply/max8971-charger/fast_charge_timer
+Date:		May 2025
+KernelVersion:	6.15.0
+Contact:	Svyatoslav Ryhel <[email protected]>
+Description:
+		This entry shows and sets the maximum time the max8971
+		charger operates in fast-charge mode. When the timer expires
+		the device will terminate fast-charge mode (charging current
+		will drop to 0 A) and will trigger interrupt.
+
+		Valid values:
+
+		- 4 - 10 (hours), step by 1
+		- 0: disabled.
+
+What:		/sys/class/power_supply/max8971-charger/top_off_threshold_current
+Date:		May 2025
+KernelVersion:	6.15.0
+Contact:	Svyatoslav Ryhel <[email protected]>
+Description:
+		This entry shows and sets the charging current threshold for
+		entering top-off charging mode. When charging current in fast
+		charge mode drops below this value, the charger will trigger
+		interrupt and start top-off charging mode.
+
+		Valid values:
+
+		- 50000 - 200000 (microamps), step by 50000 (rounded down)
+
+What:		/sys/class/power_supply/max8971-charger/top_off_timer
+Date:		May 2025
+KernelVersion:	6.15.0
+Contact:	Svyatoslav Ryhel <[email protected]>
+Description:
+		This entry shows and sets the maximum time the max8971
+		charger operates in top-off charge mode. When the timer expires
+		the device will terminate top-off charge mode (charging current
+		will drop to 0 A) and will trigger interrupt.
+
+		Valid values:
+
+		- 0 - 70 (minutes), step by 10 (rounded down)

drivers/power/supply/Kconfig

@@ -617,6 +617,20 @@ config CHARGER_MAX77976
 	  This driver can also be built as a module. If so, the module will be
 	  called max77976_charger.
 
+config CHARGER_MAX8971
+	tristate "Maxim MAX8971 battery charger driver"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  The MAX8971 is a compact, high-frequency, high-efficiency switch-mode
+	  charger for a one-cell lithium-ion (Li+) battery. It delivers up to
+	  1.55A of current to the battery from inputs up to 7.5V and withstands
+	  transient inputs up to 22V.
+
+	  Say Y to enable support for the Maxim MAX8971 battery charger.
+	  This driver can also be built as a module. If so, the module will be
+	  called max8971_charger.
+
 config CHARGER_MAX8997
 	tristate "Maxim MAX8997/MAX8966 PMIC battery charger driver"
 	depends on MFD_MAX8997 && REGULATOR_MAX8997

drivers/power/supply/Makefile

@@ -83,6 +83,7 @@ obj-$(CONFIG_CHARGER_MAX77650)	+= max77650-charger.o
 obj-$(CONFIG_CHARGER_MAX77693)	+= max77693_charger.o
 obj-$(CONFIG_CHARGER_MAX77705)	+= max77705_charger.o
 obj-$(CONFIG_CHARGER_MAX77976)	+= max77976_charger.o
+obj-$(CONFIG_CHARGER_MAX8971)	+= max8971_charger.o
 obj-$(CONFIG_CHARGER_MAX8997)	+= max8997_charger.o
 obj-$(CONFIG_CHARGER_MAX8998)	+= max8998_charger.o
 obj-$(CONFIG_CHARGER_MP2629)	+= mp2629_charger.o