regulator: Add regmap helper for ramp-delay setting

Quite a few regulator ICs do support setting ramp-delay by writing a value
matching the delay to a ramp-delay register.

Provide a simple helper for table-based delay setting.
Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Link: https://lore.kernel.org/r/f101f1db564cf32cb58719c77af0b00d7236bb89.1617020713.git.matti.vaittinen@fi.rohmeurope.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/helpers.c

@@ -901,3 +901,68 @@ bool regulator_is_equal(struct regulator *reg1, struct regulator *reg2)
 	return reg1->rdev == reg2->rdev;
 }
 EXPORT_SYMBOL_GPL(regulator_is_equal);
+
+static int find_closest_bigger(unsigned int target, const unsigned int *table,
+			       unsigned int num_sel, unsigned int *sel)
+{
+	unsigned int s, tmp, max, maxsel = 0;
+	bool found = false;
+
+	max = table[0];
+
+	for (s = 0; s < num_sel; s++) {
+		if (table[s] > max) {
+			max = table[s];
+			maxsel = s;
+		}
+		if (table[s] >= target) {
+			if (!found || table[s] - target < tmp - target) {
+				tmp = table[s];
+				*sel = s;
+				found = true;
+				if (tmp == target)
+					break;
+			}
+		}
+	}
+
+	if (!found) {
+		*sel = maxsel;
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/**
+ * regulator_set_ramp_delay_regmap - set_ramp_delay() helper
+ *
+ * @rdev: regulator to operate on
+ *
+ * Regulators that use regmap for their register I/O can set the ramp_reg
+ * and ramp_mask fields in their descriptor and then use this as their
+ * set_ramp_delay operation, saving some code.
+ */
+int regulator_set_ramp_delay_regmap(struct regulator_dev *rdev, int ramp_delay)
+{
+	int ret;
+	unsigned int sel;
+
+	if (!rdev->desc->n_ramp_values)
+		return -EINVAL;
+
+	ret = find_closest_bigger(ramp_delay, rdev->desc->ramp_delay_table,
+				  rdev->desc->n_ramp_values, &sel);
+
+	if (ret) {
+		dev_warn(rdev_get_dev(rdev),
+			 "Can't set ramp-delay %u, setting %u\n", ramp_delay,
+			 rdev->desc->ramp_delay_table[sel]);
+	}
+
+	sel <<= ffs(rdev->desc->ramp_mask) - 1;
+
+	return regmap_update_bits(rdev->regmap, rdev->desc->ramp_reg,
+				  rdev->desc->ramp_mask, sel);
+}
+EXPORT_SYMBOL_GPL(regulator_set_ramp_delay_regmap);

include/linux/regulator/driver.h

@@ -373,6 +373,10 @@ struct regulator_desc {
 	unsigned int pull_down_reg;
 	unsigned int pull_down_mask;
 	unsigned int pull_down_val_on;
+	unsigned int ramp_reg;
+	unsigned int ramp_mask;
+	const unsigned int *ramp_delay_table;
+	unsigned int n_ramp_values;
 
 	unsigned int enable_time;
 
@@ -535,6 +539,7 @@ int regulator_set_current_limit_regmap(struct regulator_dev *rdev,
 				       int min_uA, int max_uA);
 int regulator_get_current_limit_regmap(struct regulator_dev *rdev);
 void *regulator_get_init_drvdata(struct regulator_init_data *reg_init_data);
+int regulator_set_ramp_delay_regmap(struct regulator_dev *rdev, int ramp_delay);
 
 /*
  * Helper functions intended to be used by regulator drivers prior registering