[nrf fromtree] drivers: regulator: npm1300: workaround for LDO HW bug

There is a HW bug in nPM1300 LDO which causes the LDO output voltage to
reach its target very slowly in specific cases. This is worked around by
performing an additional i2c read shortly after an LDO is enabled.

Signed-off-by: Sergei Ovchinnikov <[email protected]>
(cherry picked from commit 2d34358)

Author: seov-nordic

drivers/regulator/regulator_npm1300.c

@@ -87,6 +87,7 @@ struct regulator_npm1300_config {
 	struct gpio_dt_spec retention_gpios;
 	struct gpio_dt_spec pwm_gpios;
 	uint8_t soft_start;
+	bool ldo_disable_workaround;
 };
 
 struct regulator_npm1300_data {
@@ -357,19 +358,35 @@ int regulator_npm1300_set_mode(const struct device *dev, regulator_mode_t mode)
 int regulator_npm1300_enable(const struct device *dev)
 {
 	const struct regulator_npm1300_config *config = dev->config;
+	int ret;
 
 	switch (config->source) {
 	case NPM1300_SOURCE_BUCK1:
 		return mfd_npm1300_reg_write(config->mfd, BUCK_BASE, BUCK_OFFSET_EN_SET, 1U);
 	case NPM1300_SOURCE_BUCK2:
 		return mfd_npm1300_reg_write(config->mfd, BUCK_BASE, BUCK_OFFSET_EN_SET + 2U, 1U);
 	case NPM1300_SOURCE_LDO1:
-		return mfd_npm1300_reg_write(config->mfd, LDSW_BASE, LDSW_OFFSET_EN_SET, 1U);
+		ret = mfd_npm1300_reg_write(config->mfd, LDSW_BASE, LDSW_OFFSET_EN_SET, 1U);
+		break;
 	case NPM1300_SOURCE_LDO2:
-		return mfd_npm1300_reg_write(config->mfd, LDSW_BASE, LDSW_OFFSET_EN_SET + 2U, 1U);
+		ret = mfd_npm1300_reg_write(config->mfd, LDSW_BASE, LDSW_OFFSET_EN_SET + 2U, 1U);
+		break;
 	default:
 		return 0;
 	}
+
+	if (ret < 0) {
+		return ret;
+	}
+
+	if (!config->ldo_disable_workaround) {
+		uint8_t unused;
+
+		k_msleep(2);
+		return mfd_npm1300_reg_read(config->mfd, LDSW_BASE, LDSW_OFFSET_STATUS, &unused);
+	}
+
+	return ret;
 }
 
 int regulator_npm1300_disable(const struct device *dev)
@@ -655,7 +672,8 @@ static DEVICE_API(regulator, api) = {
 		.soft_start = DT_ENUM_IDX_OR(node_id, soft_start_microamp, UINT8_MAX),             \
 		.enable_gpios = GPIO_DT_SPEC_GET_OR(node_id, enable_gpios, {0}),                   \
 		.retention_gpios = GPIO_DT_SPEC_GET_OR(node_id, retention_gpios, {0}),             \
-		.pwm_gpios = GPIO_DT_SPEC_GET_OR(node_id, pwm_gpios, {0})};                        \
+		.pwm_gpios = GPIO_DT_SPEC_GET_OR(node_id, pwm_gpios, {0}),                         \
+		.ldo_disable_workaround = DT_PROP(node_id, nordic_ldo_disable_workaround)};        \
                                                                                                    \
 	DEVICE_DT_DEFINE(node_id, regulator_npm1300_init, NULL, &data_##id, &config_##id,          \
 			 POST_KERNEL, CONFIG_REGULATOR_NPM1300_INIT_PRIORITY, &api);

dts/bindings/regulator/nordic,npm1300-regulator.yaml

@@ -96,3 +96,12 @@ child-binding:
         - 50000
       description: |
         Soft start current limit in microamps.
+
+    nordic,ldo-disable-workaround:
+      type: boolean
+      description: |
+        Disable the SW workaround for LDO bug.
+        When nPM1300 is in ULP mode, LDO is supplied from VSYS and
+        then LDO is enabled, it can take long time until the LDO
+        output has reached its target voltage. To avoid this, an i2c
+        read is performed shortly after an LDO is enabled.