regulator: Add a routine to set the current limit for QCOM PMIC VBUS

Add hooks to regulator_get_current_limit_regmap() and
regulator_set_current_limit_regmap() with an accompanying map of amperages.

This lets us use the existing helper functions to map requested current
settings to register bit-map/indicies.

This change is required to elevate the default 2 Amps set by the bootloader
to 3 Amps or indeed to constrain the value lower as the system design may
dictate.

The valid range is 500 mA to 3 A in increments of 500 mA.

Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Link: https://lore.kernel.org/r/20210427130712.2005456-2-bryan.odonoghue@linaro.orgSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/qcom_usb_vbus-regulator.c

@@ -16,13 +16,21 @@
 
 #define CMD_OTG				0x40
 #define OTG_EN				BIT(0)
+#define OTG_CURRENT_LIMIT_CFG		0x52
+#define OTG_CURRENT_LIMIT_MASK		GENMASK(2, 0)
 #define OTG_CFG				0x53
 #define OTG_EN_SRC_CFG			BIT(1)
 
+static const unsigned int curr_table[] = {
+	500000, 1000000, 1500000, 2000000, 2500000, 3000000,
+};
+
 static const struct regulator_ops qcom_usb_vbus_reg_ops = {
 	.enable = regulator_enable_regmap,
 	.disable = regulator_disable_regmap,
 	.is_enabled = regulator_is_enabled_regmap,
+	.get_current_limit = regulator_get_current_limit_regmap,
+	.set_current_limit = regulator_set_current_limit_regmap,
 };
 
 static struct regulator_desc qcom_usb_vbus_rdesc = {
@@ -30,6 +38,8 @@ static struct regulator_desc qcom_usb_vbus_rdesc = {
 	.ops = &qcom_usb_vbus_reg_ops,
 	.owner = THIS_MODULE,
 	.type = REGULATOR_VOLTAGE,
+	.curr_table = curr_table,
+	.n_current_limits = ARRAY_SIZE(curr_table),
 };
 
 static int qcom_usb_vbus_regulator_probe(struct platform_device *pdev)
@@ -61,6 +71,8 @@ static int qcom_usb_vbus_regulator_probe(struct platform_device *pdev)
 
 	qcom_usb_vbus_rdesc.enable_reg = base + CMD_OTG;
 	qcom_usb_vbus_rdesc.enable_mask = OTG_EN;
+	qcom_usb_vbus_rdesc.csel_reg = base + OTG_CURRENT_LIMIT_CFG;
+	qcom_usb_vbus_rdesc.csel_mask = OTG_CURRENT_LIMIT_MASK;
 	config.dev = dev;
 	config.init_data = init_data;
 	config.of_node = dev->of_node;