mfd: rk808: Disable the under voltage detect

Rk808 has a under voltage detect function, when the voltage of buck is
under 85% the target voltage, the buck output will reset. But if the
power load is too heavy, this function maybe err, when current over
4.2A, although the voltage is normal, but RK808 mistakenly think it is
under 85%, and reset the buck. So let's disable this function.
Signed-off-by: Chris Zhong <zyw@rock-chips.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/rk808.c

@@ -89,6 +89,7 @@ static const struct rk808_reg_data pre_init_reg[] = {
 	{ RK808_BOOST_CONFIG_REG, BOOST_ILMIN_MASK, BOOST_ILMIN_100MA },
 	{ RK808_BUCK1_CONFIG_REG, BUCK1_RATE_MASK,  BUCK_ILMIN_200MA },
 	{ RK808_BUCK2_CONFIG_REG, BUCK2_RATE_MASK,  BUCK_ILMIN_200MA },
+	{ RK808_DCDC_UV_ACT_REG,  BUCK_UV_ACT_MASK, BUCK_UV_ACT_DISABLE},
 	{ RK808_VB_MON_REG,       MASK_ALL,         VB_LO_ACT |
 						    VB_LO_SEL_3500MV },
 };

include/linux/mfd/rk808.h

@@ -156,6 +156,9 @@ enum rk808_reg {
 #define BUCK2_RATE_MASK		(3 << 3)
 #define MASK_ALL	0xff
 
+#define BUCK_UV_ACT_MASK	0x0f
+#define BUCK_UV_ACT_DISABLE	0
+
 #define SWITCH2_EN	BIT(6)
 #define SWITCH1_EN	BIT(5)
 #define DEV_OFF_RST	BIT(3)