regulator: qcom-labibb: Implement current limiting

LAB and IBB regulators can be current-limited by setting the
appropriate registers, but this operation is granted only after
sending an unlock code for secure access.

Besides the secure access, it would be possible to use the
regmap helper for get_current_limit, as there is no security
blocking reads, but I chose not to as to avoid having a very
big array containing current limits, especially for IBB.

That said, these regulators support current limiting for:
- LAB (pos): 200-1600mA, with 200mA per step (8 steps),
- IBB (neg):   0-1550mA, with  50mA per step (32 steps).

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Link: https://lore.kernel.org/r/20210119174421.226541-3-angelogioacchino.delregno@somainline.org
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/qcom-labibb-regulator.c

@@ -29,6 +29,15 @@
 #define LABIBB_STATUS1_VREG_OK_BIT	BIT(7)
 #define LABIBB_CONTROL_ENABLE		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_LABIBB_SEC_ACCESS		0xd0
+ #define LABIBB_SEC_UNLOCK_CODE		0xa5
+
 #define LAB_ENABLE_CTL_MASK		BIT(7)
 #define IBB_ENABLE_CTL_MASK		(BIT(7) | BIT(6))
 
@@ -37,11 +46,18 @@
 #define IBB_ENABLE_TIME			(LABIBB_OFF_ON_DELAY * 10)
 #define LABIBB_POLL_ENABLED_TIME	1000
 
+struct labibb_current_limits {
+	u32				uA_min;
+	u32				uA_step;
+	u8				ovr_val;
+};
+
 struct labibb_regulator {
 	struct regulator_desc		desc;
 	struct device			*dev;
 	struct regmap			*regmap;
 	struct regulator_dev		*rdev;
+	struct labibb_current_limits	uA_limits;
 	u16				base;
 	u8				type;
 };
@@ -53,6 +69,57 @@ struct labibb_regulator_data {
 	const struct regulator_desc	*desc;
 };
 
+static int qcom_labibb_set_current_limit(struct regulator_dev *rdev,
+					 int min_uA, int max_uA)
+{
+	struct labibb_regulator *vreg = rdev_get_drvdata(rdev);
+	struct regulator_desc *desc = &vreg->desc;
+	struct labibb_current_limits *lim = &vreg->uA_limits;
+	u32 mask, val;
+	int i, ret, sel = -1;
+
+	if (min_uA < lim->uA_min || max_uA < lim->uA_min)
+		return -EINVAL;
+
+	for (i = 0; i < desc->n_current_limits; i++) {
+		int uA_limit = (lim->uA_step * i) + lim->uA_min;
+
+		if (max_uA >= uA_limit && min_uA <= uA_limit)
+			sel = i;
+	}
+	if (sel < 0)
+		return -EINVAL;
+
+	/* Current limit setting needs secure access */
+	ret = regmap_write(vreg->regmap, vreg->base + REG_LABIBB_SEC_ACCESS,
+			   LABIBB_SEC_UNLOCK_CODE);
+	if (ret)
+		return ret;
+
+	mask = desc->csel_mask | lim->ovr_val;
+	mask |= LABIBB_CURRENT_LIMIT_EN;
+	val = (u32)sel | lim->ovr_val;
+	val |= LABIBB_CURRENT_LIMIT_EN;
+
+	return regmap_update_bits(vreg->regmap, desc->csel_reg, mask, val);
+}
+
+static int qcom_labibb_get_current_limit(struct regulator_dev *rdev)
+{
+	struct labibb_regulator *vreg = rdev_get_drvdata(rdev);
+	struct regulator_desc *desc = &vreg->desc;
+	struct labibb_current_limits *lim = &vreg->uA_limits;
+	unsigned int cur_step;
+	int ret;
+
+	ret = regmap_read(vreg->regmap, desc->csel_reg, &cur_step);
+	if (ret)
+		return ret;
+	cur_step &= desc->csel_mask;
+
+	return (cur_step * lim->uA_step) + lim->uA_min;
+}
+
 static const struct regulator_ops qcom_labibb_ops = {
 	.enable			= regulator_enable_regmap,
 	.disable		= regulator_disable_regmap,
@@ -61,6 +128,8 @@ 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_current_limit	= qcom_labibb_set_current_limit,
+	.get_current_limit	= qcom_labibb_get_current_limit,
 };
 
 static const struct regulator_desc pmi8998_lab_desc = {
@@ -73,6 +142,9 @@ static const struct regulator_desc pmi8998_lab_desc = {
 	.vsel_mask		= LAB_VOLTAGE_SET_MASK,
 	.apply_reg		= (PMI8998_LAB_REG_BASE + REG_LABIBB_VOLTAGE),
 	.apply_bit		= LABIBB_VOLTAGE_OVERRIDE_EN,
+	.csel_reg		= (PMI8998_LAB_REG_BASE + REG_LABIBB_CURRENT_LIMIT),
+	.csel_mask		= LAB_CURRENT_LIMIT_MASK,
+	.n_current_limits	= 8,
 	.off_on_delay		= LABIBB_OFF_ON_DELAY,
 	.owner			= THIS_MODULE,
 	.type			= REGULATOR_VOLTAGE,
@@ -92,6 +164,9 @@ static const struct regulator_desc pmi8998_ibb_desc = {
 	.vsel_mask		= IBB_VOLTAGE_SET_MASK,
 	.apply_reg		= (PMI8998_IBB_REG_BASE + REG_LABIBB_VOLTAGE),
 	.apply_bit		= LABIBB_VOLTAGE_OVERRIDE_EN,
+	.csel_reg		= (PMI8998_IBB_REG_BASE + REG_LABIBB_CURRENT_LIMIT),
+	.csel_mask		= IBB_CURRENT_LIMIT_MASK,
+	.n_current_limits	= 32,
 	.off_on_delay		= LABIBB_OFF_ON_DELAY,
 	.owner			= THIS_MODULE,
 	.type			= REGULATOR_VOLTAGE,
@@ -163,6 +238,23 @@ static int qcom_labibb_regulator_probe(struct platform_device *pdev)
 		vreg->base = reg_data->base;
 		vreg->type = reg_data->type;
 
+		switch (vreg->type) {
+		case QCOM_LAB_TYPE:
+			/* LAB Limits: 200-1600mA */
+			vreg->uA_limits.uA_min  = 200000;
+			vreg->uA_limits.uA_step = 200000;
+			vreg->uA_limits.ovr_val = LAB_CURRENT_LIMIT_OVERRIDE_EN;
+			break;
+		case QCOM_IBB_TYPE:
+			/* IBB Limits: 0-1550mA */
+			vreg->uA_limits.uA_min  = 0;
+			vreg->uA_limits.uA_step = 50000;
+			vreg->uA_limits.ovr_val = 0; /* No override bit */
+			break;
+		default:
+			return -EINVAL;
+		}
+
 		memcpy(&vreg->desc, reg_data->desc, sizeof(vreg->desc));
 		vreg->desc.of_match = reg_data->name;
 		vreg->desc.name = reg_data->name;