power_supply: Add TI BQ24257 charger driver

Based on the datasheet found here:
http://www.ti.com/lit/ds/symlink/bq24257.pdfSigned-off-by: Laurentiu Palcu <laurentiu.palcu@intel.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski.k@gmail.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

Documentation/devicetree/bindings/power/bq24257.txt

+Binding for TI bq24257 Li-Ion Charger
+
+Required properties:
+- compatible: Should contain one of the following:
+ * "ti,bq24257"
+- reg:			   integer, i2c address of the device.
+- ti,battery-regulation-voltage: integer, maximum charging voltage in uV.
+- ti,charge-current:	   integer, maximum charging current in uA.
+- ti,termination-current:  integer, charge will be terminated when current in
+			   constant-voltage phase drops below this value (in uA).
+
+Example:
+
+bq24257 {
+	compatible = "ti,bq24257";
+	reg = <0x6a>;
+
+	ti,battery-regulation-voltage = <4200000>;
+	ti,charge-current = <1000000>;
+	ti,termination-current = <50000>;
+};

drivers/power/Kconfig

@@ -388,6 +388,13 @@ config CHARGER_BQ24190
 	help
 	  Say Y to enable support for the TI BQ24190 battery charger.
 
+config CHARGER_BQ24257
+	tristate "TI BQ24257 battery charger driver"
+	depends on I2C && GPIOLIB
+	depends on REGMAP_I2C
+	help
+	  Say Y to enable support for the TI BQ24257 battery charger.
+
 config CHARGER_BQ24735
 	tristate "TI BQ24735 battery charger support"
 	depends on I2C && GPIOLIB

drivers/power/Makefile

@@ -58,6 +58,7 @@ obj-$(CONFIG_CHARGER_MAX8997)	+= max8997_charger.o
 obj-$(CONFIG_CHARGER_MAX8998)	+= max8998_charger.o
 obj-$(CONFIG_CHARGER_BQ2415X)	+= bq2415x_charger.o
 obj-$(CONFIG_CHARGER_BQ24190)	+= bq24190_charger.o
+obj-$(CONFIG_CHARGER_BQ24257)	+= bq24257_charger.o
 obj-$(CONFIG_CHARGER_BQ24735)	+= bq24735-charger.o
 obj-$(CONFIG_POWER_AVS)		+= avs/
 obj-$(CONFIG_CHARGER_SMB347)	+= smb347-charger.o