regulator: add driver for hi6421 voltage regulator

Add driver support for HiSilicon Hi6421 voltage regulators.

Two rules for regulator enabling are defined in hi6421 spec:
1) Between disable and enable of each regulator (LDOs or BUCKs), there must
   be a protection gap. Use @off_on_delay of regulator core to implement this.
2) No two regulators can be enabled at the same time. Use mutex in
   hi6421_regulator_pdata to ensure this. A protection gap of 100us is added
   into each LDO/BUCK's .enable_time.
Signed-off-by: Guodong Xu <guodong.xu@linaro.org>
Signed-off-by: Mark Brown <broonie@linaro.org>

drivers/regulator/Kconfig

@@ -240,6 +240,16 @@ config REGULATOR_GPIO
 	  and the platform has to provide a mapping of GPIO-states
 	  to target volts/amps.
 
+config REGULATOR_HI6421
+	tristate "HiSilicon Hi6421 PMIC voltage regulator support"
+	depends on MFD_HI6421_PMIC && OF
+	help
+	  This driver provides support for the voltage regulators on the
+	  HiSilicon Hi6421 PMU / Codec IC.
+	  Hi6421 is a multi-function device which, on regulator part, provides
+	  21 general purpose LDOs, 3 dedicated LDOs, and 5 BUCKs. All
+	  of them come with support to either ECO (idle) or sleep mode.
+
 config REGULATOR_ISL6271A
 	tristate "Intersil ISL6271A Power regulator"
 	depends on I2C

drivers/regulator/Makefile

@@ -32,6 +32,7 @@ obj-$(CONFIG_REGULATOR_DBX500_PRCMU) += dbx500-prcmu.o
 obj-$(CONFIG_REGULATOR_DB8500_PRCMU) += db8500-prcmu.o
 obj-$(CONFIG_REGULATOR_FAN53555) += fan53555.o
 obj-$(CONFIG_REGULATOR_GPIO) += gpio-regulator.o
+obj-$(CONFIG_REGULATOR_HI6421) += hi6421-regulator.o
 obj-$(CONFIG_REGULATOR_ISL6271A) += isl6271a-regulator.o
 obj-$(CONFIG_REGULATOR_LP3971) += lp3971.o
 obj-$(CONFIG_REGULATOR_LP3972) += lp3972.o