[PATCH v2 4/5] regulator: Support the LTM8054 voltage regulator

[Romain Gantois <romain.gantois@bootlin.com>]

Add a stub driver for the  Linear Technology LTM8054 Buck-Boost voltage
regulator. This version only supports enabling/disabling the regulator via
a GPIO, and reporting the output voltage level from the resistor divider
values given in the device tree.

Signed-off-by: Romain Gantois <romain.gantois@bootlin.com>
---
 MAINTAINERS                           |   1 +
 drivers/regulator/Kconfig             |   8 +++
 drivers/regulator/Makefile            |   1 +
 drivers/regulator/ltm8054-regulator.c | 126 ++++++++++++++++++++++++++++++++++
 4 files changed, 136 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 69bcba82808bb815af436232fab50f70713fd533..310dac4f60ab1e6e82e4dd667482f46723964992 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14538,6 +14538,7 @@ LTM8054 REGULATOR DRIVER
 M:	Romain Gantois <romain.gantois@bootlin.com>
 S:	Maintained
 F:	Documentation/devicetree/bindings/regulator/adi,ltm8054.yaml
+F:	drivers/regulator/ltm8054-regulator.c
 
 LTP (Linux Test Project)
 M:	Andrea Cervesato <andrea.cervesato@suse.com>
diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
index e252bb11ae6615dc9154908bc237905b97e739e5..c48b2af350974b3715a1ecf05dec656a92268294 100644
--- a/drivers/regulator/Kconfig
+++ b/drivers/regulator/Kconfig
@@ -577,6 +577,14 @@ config REGULATOR_LTC3676
 	  This enables support for the LTC3676
 	  8-output regulators controlled via I2C.
 
+config REGULATOR_LTM8054
+	tristate "LTM8054 Buck-Boost voltage regulator"
+	help
+	  This driver provides support for the Analog Devices LTM8054
+	  Buck-Boost micromodule regulator. The LTM8054 has an adjustable
+	  output current limitation and a feedback pin for setting the
+	  output voltage level.
+
 config REGULATOR_MAX14577
 	tristate "Maxim 14577/77836 regulator"
 	depends on MFD_MAX14577
diff --git a/drivers/regulator/Makefile b/drivers/regulator/Makefile
index 76b02d12b758c607028d2c8879017afc6d1b244e..afcc9ffcc72f268a9e999a185e3024d67261249a 100644
--- a/drivers/regulator/Makefile
+++ b/drivers/regulator/Makefile
@@ -70,6 +70,7 @@ obj-$(CONFIG_REGULATOR_LP8788) += lp8788-ldo.o
 obj-$(CONFIG_REGULATOR_LP8755) += lp8755.o
 obj-$(CONFIG_REGULATOR_LTC3589) += ltc3589.o
 obj-$(CONFIG_REGULATOR_LTC3676) += ltc3676.o
+obj-$(CONFIG_REGULATOR_LTM8054) += ltm8054-regulator.o
 obj-$(CONFIG_REGULATOR_MAX14577) += max14577-regulator.o
 obj-$(CONFIG_REGULATOR_MAX1586) += max1586.o
 obj-$(CONFIG_REGULATOR_MAX5970) += max5970-regulator.o
diff --git a/drivers/regulator/ltm8054-regulator.c b/drivers/regulator/ltm8054-regulator.c
new file mode 100644
index 0000000000000000000000000000000000000000..bc8cf98b5a3b5663481d148330de70a8165e5981
--- /dev/null
+++ b/drivers/regulator/ltm8054-regulator.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Analog Devices LTM8054 Buck-Boost regulator driver
+ *
+ * Copyright (C) 2025 Bootlin
+ */
+
+#include <asm/div64.h>
+
+#include <linux/array_size.h>
+
+#include <linux/device.h>
+#include <linux/device/devres.h>
+#include <linux/device/driver.h>
+
+#include <linux/dev_printk.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+
+#include <linux/regulator/consumer.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/of_regulator.h>
+
+/* The LTM8054 regulates its FB pin to 1.2V */
+#define LTM8054_FB_uV 1200000
+
+struct ltm8054_priv {
+	struct regulator_desc rdesc;
+};
+
+static int ltm8054_scale(unsigned int uV, u32 r1, u32 r2)
+{
+	u64 tmp;
+
+	tmp = (u64)uV * r1;
+	do_div(tmp, r2);
+
+	return uV + tmp;
+}
+
+static const struct regulator_ops ltm8054_regulator_ops = { };
+
+static int ltm8054_of_parse(struct device *dev, struct ltm8054_priv *priv,
+			    struct regulator_config *config)
+{
+	struct device_node *np = dev->of_node;
+	u32 r[2];
+	int ret;
+
+	config->of_node = np;
+
+	ret = device_property_read_u32_array(dev, "lltc,fb-voltage-divider", r, ARRAY_SIZE(r));
+	if (ret)
+		return ret;
+
+	priv->rdesc.fixed_uV = ltm8054_scale(LTM8054_FB_uV, r[0], r[1]);
+	priv->rdesc.min_uV = priv->rdesc.fixed_uV;
+	priv->rdesc.n_voltages = 1;
+
+	config->init_data = of_get_regulator_init_data(dev,
+						       np,
+						       &priv->rdesc);
+	if (!config->init_data)
+		return -EINVAL;
+
+	config->ena_gpiod = devm_gpiod_get_optional(dev, "enable", GPIOD_OUT_LOW);
+	if (IS_ERR(config->ena_gpiod))
+		return PTR_ERR(config->ena_gpiod);
+
+	return 0;
+}
+
+static int ltm8054_probe(struct platform_device *pdev)
+{
+	struct regulator_config config = { };
+	struct device *dev = &pdev->dev;
+	struct regulator_dev *rdev;
+	struct ltm8054_priv *priv;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->rdesc.name = "ltm8054-regulator",
+	priv->rdesc.ops = &ltm8054_regulator_ops,
+	priv->rdesc.type = REGULATOR_VOLTAGE,
+	priv->rdesc.owner = THIS_MODULE,
+
+	config.dev = dev;
+	config.driver_data = priv;
+
+	ret = ltm8054_of_parse(dev, priv, &config);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to parse device tree\n");
+
+	rdev = devm_regulator_register(dev, &priv->rdesc, &config);
+	if (IS_ERR(rdev))
+		return dev_err_probe(dev, PTR_ERR(rdev), "failed to register regulator\n");
+
+	return 0;
+}
+
+static const struct of_device_id ltm8054_of_match[] = {
+	{ .compatible = "adi,ltm8054" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, ltm8054_of_match);
+
+static struct platform_driver ltm8054_driver = {
+	.probe = ltm8054_probe,
+	.driver = {
+		.name  = "ltm8054",
+		.of_match_table = ltm8054_of_match,
+	},
+};
+module_platform_driver(ltm8054_driver);
+
+MODULE_DESCRIPTION("LTM8054 regulator driver");
+MODULE_AUTHOR("Romain Gantois <romain.gantois@bootlin.com>");
+MODULE_LICENSE("GPL");

-- 
2.51.0