regulator: mp8859: Implement set_current_limit()

The mp8859 implements support for current limiting, provide support for
configuring this via the driver. The datasheet recommends that if the
device has hit the current limit then any changes should be implemented
via a ramp so we do so in the driver.

Tested-by: Markus Reichl <m.reichl@fivetechno.de>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://msgid.link/r/20240225-regulator-mp8859-v1-8-68ee2c839ded@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: broonie

drivers/regulator/mp8859.c

@@ -35,6 +35,8 @@
 
 #define MP8859_GO_BIT			0x01
 
+#define MP8859_IOUT_LIM_MASK		0x7f
+
 #define MP8859_ENABLE_MASK		0x80
 #define MP8859_DISCHG_EN_MASK		0x10
 #define MP8859_MODE_MASK		0x08
@@ -131,6 +133,58 @@ static int mp8859_set_mode(struct regulator_dev *rdev, unsigned int mode)
 				  MP8859_MODE_MASK, val);
 }
 
+static int mp8859_set_current_limit(struct regulator_dev *rdev,
+				    int min_uA, int max_uA)
+{
+	unsigned int cur_val, new_val;
+	int ret, i;
+
+	/* Steps of 50mA */
+	new_val = max_uA / 50000;
+	if (new_val > MP8859_IOUT_LIM_MASK)
+		return -EINVAL;
+	if (new_val == 0)
+		return -EINVAL;
+
+	/*
+	 * If the regulator is limiting then ramp gradually as per
+	 * datasheet, otherwise just set the value directly.
+	 */
+	ret = regmap_read(rdev->regmap, MP8859_STATUS_REG, &cur_val);
+	if (ret != 0)
+		return ret;
+	if (!(cur_val & MP8859_CC_CV_MASK)) {
+		return regmap_update_bits(rdev->regmap, MP8859_IOUT_LIM_REG,
+					  MP8859_IOUT_LIM_MASK, new_val);
+	}
+
+	ret = regmap_read(rdev->regmap, MP8859_IOUT_LIM_REG, &cur_val);
+	if (ret != 0)
+		return ret;
+
+	if (cur_val >= new_val) {
+		for (i = cur_val; i >= new_val; i--) {
+			ret = regmap_update_bits(rdev->regmap,
+						 MP8859_IOUT_LIM_REG,
+						 MP8859_IOUT_LIM_MASK,
+						 cur_val - i);
+			if (ret != 0)
+				return ret;
+		}
+	} else {
+		for (i = cur_val; i <= new_val; i++) {
+			ret = regmap_update_bits(rdev->regmap,
+						 MP8859_IOUT_LIM_REG,
+						 MP8859_IOUT_LIM_MASK,
+						 cur_val + i);
+			if (ret != 0)
+				return ret;
+		}
+	}
+
+	return 0;
+}
+
 static int mp8859_get_status(struct regulator_dev *rdev)
 {
 	unsigned int val;
@@ -241,6 +295,7 @@ static const struct regulator_ops mp8859_ops = {
 	.set_mode = mp8859_set_mode,
 	.get_mode = mp8859_get_mode,
 	.set_active_discharge = regulator_set_active_discharge_regmap,
+	.set_current_limit = mp8859_set_current_limit,
 	.get_status = mp8859_get_status,
 	.get_error_flags = mp8859_get_error_flags,
 };