drivers: adp536x: Add buck discharge resistor configuration

This patch adds buck discharge resistor configuration
functionality to the ADP536x driver.

Signed-off-by: Jan Tore Guggedal <jantore.guggedal@nordicsemi.no>

drivers/adp536x/adp536x.c

@@ -24,6 +24,7 @@
 #define ADP536X_CHG_STATUS_2				0x09
 #define ADP536X_BAT_PROTECT_CTRL			0x11
 #define ADP536X_BAT_OC_CHG				0x15
+#define ADP536X_BUCK_CFG				0x29
 #define ADP536X_BUCK_OUTPUT				0x2A
 #define ADP536X_BUCKBST_CFG				0x2B
 #define ADP536X_BUCKBST_OUTPUT				0x2C
@@ -112,6 +113,10 @@
 #define ADP536X_BAT_OC_CHG_DGT_OC_CHG_MSK		GENMASK(4, 3)
 #define ADP536X_BAT_OC_CHG_DGT_OC_CHG(x)		(((x) & 0x03) << 3)
 
+/* Buck configure register. */
+#define ADP536X_BUCK_CFG_DISCHG_BUCK_MSK		BIT(1)
+#define ADP536X_BUCK_CFG_DISCHG_BUCK(x)			(((x) & 0x01) << 1)
+
 /* Buck output voltage setting register. */
 #define ADP536X_BUCK_OUTPUT_VOUT_BUCK_MSK		GENMASK(5, 0)
 #define ADP536X_BUCK_OUTPUT_VOUT_BUCK(x)		(((x) & 0x3F) << 0)
@@ -239,6 +244,13 @@ int adp536x_buck_1v8_set(void)
 					ADP536X_BUCK_OUTPUT_VOUT_BUCK(value));
 }
 
+int adp536x_buck_discharge_set(bool enable)
+{
+	return adp536x_reg_write_mask(ADP536X_BUCK_CFG,
+				ADP536X_BUCK_CFG_DISCHG_BUCK_MSK,
+				ADP536X_BUCK_CFG_DISCHG_BUCK(enable));
+}
+
 int adp536x_buckbst_3v3_set(void)
 {
 	/* 3.3V equals to 0b10011 = 0x13, according to ADP536X datasheet. */

include/drivers/adp536x.h

@@ -20,3 +20,4 @@ int adp536x_buck_1v8_set(void);
 int adp536x_buckbst_3v3_set(void);
 int adp536x_factory_reset(void);
 int adp536x_oc_chg_current_set(u8_t value);
+int adp536x_buck_discharge_set(bool enable);