regulator: qcom-labibb: Implement pull-down, softstart, active discharge

Soft start is required to avoid inrush current during LAB ramp-up and
IBB ramp-down, protecting connected hardware to which we supply voltage.

Since soft start is configurable on both LAB and IBB regulators, it
was necessary to add two DT properties, respectively "qcom,soft-start-us"
to control LAB ramp-up and "qcom,discharge-resistor-kohms" to control
the discharge resistor for IBB ramp-down, which obviously brought the
need of implementing a of_parse callback for both regulators.

Finally, also implement pull-down mode in order to avoid unpredictable
behavior when the regulators are disabled (random voltage spikes etc).

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20210119174421.226541-4-angelogioacchino.delregno@somainline.org
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: kholk

drivers/regulator/qcom-labibb-regulator.c

@@ -29,12 +29,23 @@
 #define LABIBB_STATUS1_VREG_OK_BIT	BIT(7)
 #define LABIBB_CONTROL_ENABLE		BIT(7)
 
+#define REG_LABIBB_PD_CTL		0x47
+ #define LAB_PD_CTL_MASK		GENMASK(1, 0)
+ #define IBB_PD_CTL_MASK		(BIT(0) | BIT(7))
+ #define LAB_PD_CTL_STRONG_PULL		BIT(0)
+ #define IBB_PD_CTL_HALF_STRENGTH	BIT(0)
+ #define IBB_PD_CTL_EN			BIT(7)
+
 #define REG_LABIBB_CURRENT_LIMIT	0x4b
  #define LAB_CURRENT_LIMIT_MASK		GENMASK(2, 0)
  #define IBB_CURRENT_LIMIT_MASK		GENMASK(4, 0)
  #define LAB_CURRENT_LIMIT_OVERRIDE_EN	BIT(3)
  #define LABIBB_CURRENT_LIMIT_EN	BIT(7)
 
+#define REG_IBB_PWRUP_PWRDN_CTL_1	0x58
+ #define IBB_CTL_1_DISCHARGE_EN		BIT(2)
+
+#define REG_LABIBB_SOFT_START_CTL	0x5f
 #define REG_LABIBB_SEC_ACCESS		0xd0
  #define LABIBB_SEC_UNLOCK_CODE		0xa5
 
@@ -60,6 +71,8 @@ struct labibb_regulator {
 	struct labibb_current_limits	uA_limits;
 	u16				base;
 	u8				type;
+	u8				dischg_sel;
+	u8				soft_start_sel;
 };
 
 struct labibb_regulator_data {
@@ -120,6 +133,70 @@ static int qcom_labibb_get_current_limit(struct regulator_dev *rdev)
 	return (cur_step * lim->uA_step) + lim->uA_min;
 }
 
+static int qcom_labibb_set_soft_start(struct regulator_dev *rdev)
+{
+	struct labibb_regulator *vreg = rdev_get_drvdata(rdev);
+	u32 val = 0;
+
+	if (vreg->type == QCOM_IBB_TYPE)
+		val = vreg->dischg_sel;
+	else
+		val = vreg->soft_start_sel;
+
+	return regmap_write(rdev->regmap, rdev->desc->soft_start_reg, val);
+}
+
+static int qcom_labibb_get_table_sel(const int *table, int sz, u32 value)
+{
+	int i;
+
+	for (i = 0; i < sz; i++)
+		if (table[i] == value)
+			return i;
+	return -EINVAL;
+}
+
+/* IBB discharge resistor values in KOhms */
+static const int dischg_resistor_values[] = { 300, 64, 32, 16 };
+
+/* Soft start time in microseconds */
+static const int soft_start_values[] = { 200, 400, 600, 800 };
+
+static int qcom_labibb_of_parse_cb(struct device_node *np,
+				   const struct regulator_desc *desc,
+				   struct regulator_config *config)
+{
+	struct labibb_regulator *vreg = config->driver_data;
+	u32 dischg_kohms, soft_start_time;
+	int ret;
+
+	ret = of_property_read_u32(np, "qcom,discharge-resistor-kohms",
+				       &dischg_kohms);
+	if (ret)
+		dischg_kohms = 300;
+
+	ret = qcom_labibb_get_table_sel(dischg_resistor_values,
+					ARRAY_SIZE(dischg_resistor_values),
+					dischg_kohms);
+	if (ret < 0)
+		return ret;
+	vreg->dischg_sel = (u8)ret;
+
+	ret = of_property_read_u32(np, "qcom,soft-start-us",
+				   &soft_start_time);
+	if (ret)
+		soft_start_time = 200;
+
+	ret = qcom_labibb_get_table_sel(soft_start_values,
+					ARRAY_SIZE(soft_start_values),
+					soft_start_time);
+	if (ret < 0)
+		return ret;
+	vreg->soft_start_sel = (u8)ret;
+
+	return 0;
+}
+
 static const struct regulator_ops qcom_labibb_ops = {
 	.enable			= regulator_enable_regmap,
 	.disable		= regulator_disable_regmap,
@@ -128,8 +205,11 @@ static const struct regulator_ops qcom_labibb_ops = {
 	.get_voltage_sel	= regulator_get_voltage_sel_regmap,
 	.list_voltage		= regulator_list_voltage_linear,
 	.map_voltage		= regulator_map_voltage_linear,
+	.set_active_discharge	= regulator_set_active_discharge_regmap,
+	.set_pull_down		= regulator_set_pull_down_regmap,
 	.set_current_limit	= qcom_labibb_set_current_limit,
 	.get_current_limit	= qcom_labibb_get_current_limit,
+	.set_soft_start		= qcom_labibb_set_soft_start,
 };
 
 static const struct regulator_desc pmi8998_lab_desc = {
@@ -138,6 +218,10 @@ static const struct regulator_desc pmi8998_lab_desc = {
 	.enable_val		= LABIBB_CONTROL_ENABLE,
 	.enable_time		= LAB_ENABLE_TIME,
 	.poll_enabled_time	= LABIBB_POLL_ENABLED_TIME,
+	.soft_start_reg		= (PMI8998_LAB_REG_BASE + REG_LABIBB_SOFT_START_CTL),
+	.pull_down_reg		= (PMI8998_LAB_REG_BASE + REG_LABIBB_PD_CTL),
+	.pull_down_mask		= LAB_PD_CTL_MASK,
+	.pull_down_val_on	= LAB_PD_CTL_STRONG_PULL,
 	.vsel_reg		= (PMI8998_LAB_REG_BASE + REG_LABIBB_VOLTAGE),
 	.vsel_mask		= LAB_VOLTAGE_SET_MASK,
 	.apply_reg		= (PMI8998_LAB_REG_BASE + REG_LABIBB_VOLTAGE),
@@ -152,6 +236,7 @@ static const struct regulator_desc pmi8998_lab_desc = {
 	.uV_step		= 100000,
 	.n_voltages		= 16,
 	.ops			= &qcom_labibb_ops,
+	.of_parse_cb		= qcom_labibb_of_parse_cb,
 };
 
 static const struct regulator_desc pmi8998_ibb_desc = {
@@ -160,6 +245,14 @@ static const struct regulator_desc pmi8998_ibb_desc = {
 	.enable_val		= LABIBB_CONTROL_ENABLE,
 	.enable_time		= IBB_ENABLE_TIME,
 	.poll_enabled_time	= LABIBB_POLL_ENABLED_TIME,
+	.soft_start_reg		= (PMI8998_IBB_REG_BASE + REG_LABIBB_SOFT_START_CTL),
+	.active_discharge_off	= 0,
+	.active_discharge_on	= IBB_CTL_1_DISCHARGE_EN,
+	.active_discharge_mask	= IBB_CTL_1_DISCHARGE_EN,
+	.active_discharge_reg	= (PMI8998_IBB_REG_BASE + REG_IBB_PWRUP_PWRDN_CTL_1),
+	.pull_down_reg		= (PMI8998_IBB_REG_BASE + REG_LABIBB_PD_CTL),
+	.pull_down_mask		= IBB_PD_CTL_MASK,
+	.pull_down_val_on	= IBB_PD_CTL_HALF_STRENGTH | IBB_PD_CTL_EN,
 	.vsel_reg		= (PMI8998_IBB_REG_BASE + REG_LABIBB_VOLTAGE),
 	.vsel_mask		= IBB_VOLTAGE_SET_MASK,
 	.apply_reg		= (PMI8998_IBB_REG_BASE + REG_LABIBB_VOLTAGE),
@@ -174,6 +267,7 @@ static const struct regulator_desc pmi8998_ibb_desc = {
 	.uV_step		= 100000,
 	.n_voltages		= 64,
 	.ops			= &qcom_labibb_ops,
+	.of_parse_cb		= qcom_labibb_of_parse_cb,
 };
 
 static const struct labibb_regulator_data pmi8998_labibb_data[] = {