[PATCH 3/4] regulator: Support the LTM8054 voltage regulator

Romain Gantois
2025-09-16T10:24:22Z

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 | 120 ++++++++++++++++++++++++++++++++++
4 files changed, 130 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 7160179e6bf9d45a241582c1b6df8c0ebf6c3641..4bc1a0e4c087060295a927da02f56c332269035f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14521,6 +14521,7 @@ LTM8054 REGULATOR DRIVER
M: Romain Gantois <romain.gantois@bootlin.com>
S: Maintained
F: Documentation/devicetree/bindings/regulator/lltc,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 eaa6df1c9f806652a21942bcb48084ba63f942d9..15fb71193b67d0b2daa631b69778dde9323aedd2 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 Linear Technology 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 be98b29d6675d8be1ca984c2d137bdfc4ba2de87..0e61ef826c08f64ea638d19bf10e69abf1526aa7 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..e41bd95da55fb87912e2cdf70bae231133c25745
--- /dev/null
+++ b/drivers/regulator/ltm8054-regulator.c
@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Linear Technology LTM8054 Buck-Boost regulator driver
+ *
+ * Copyright (C) 2025 Bootlin
+ */
+
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/mod_devicetable.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/of_regulator.h>
+#include <linux/platform_device.h>
+#include <linux/gpio/consumer.h>
+
+/* The LTM8054 regulates its FB pin to 1.2V */
+#define LTM8054_FB_V 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 + (unsigned int)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 = of_property_read_u32_array(np, "lltc,fb-voltage-divider", r, 2);
+ if (ret) {
+ dev_err(dev, "Failed to parse voltage divider\n");
+ return ret;
+ }
+
+ priv->rdesc.fixed_uV = ltm8054_scale(LTM8054_FB_V, 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) {
+ dev_err(dev, "failed to parse init data\n");
+ return -EINVAL;
+ }
+
+ config->ena_gpiod = devm_gpiod_get_optional(dev, "enable", GPIOD_OUT_LOW);
+ if (IS_ERR(config->ena_gpiod)) {
+ dev_err(dev, "unable to acquire enable gpio\n");
+ return PTR_ERR(config->ena_gpiod);
+ }
+
+ return 0;
+}
+
+static int ltm8054_probe(struct platform_device *pdev)
+{
+ struct regulator_config config = { 0 };
+ struct regulator_dev *rdev;
+ struct ltm8054_priv *priv;
+ int ret;
+
+ priv = devm_kzalloc(&pdev->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 = &pdev->dev;
+ config.driver_data = priv;
+
+ ret = ltm8054_of_parse(&pdev->dev, priv, &config);
+ if (ret)
+ return dev_err_probe(&pdev->dev, ret, "failed to parse device tree\n");
+
+ rdev = devm_regulator_register(&pdev->dev, &priv->rdesc, &config);
+ if (IS_ERR(rdev))
+ return dev_err_probe(&pdev->dev, PTR_ERR(rdev), "failed to register regulator\n");
+
+ return 0;
+}
+
+static const struct of_device_id __maybe_unused ltm8054_of_match[] = {
+ { .compatible = "lltc,ltm8054", },
+ {},
+};
+MODULE_DEVICE_TABLE(of, ltm8054_of_match);
+
+static struct platform_driver ltm8054_driver = {
+ .probe = ltm8054_probe,
+ .driver = {
+ .name = "ltm8054",
+ .of_match_table = of_match_ptr(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