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Message-Id: <20250925-ltm8054-driver-v2-5-bb61a401a0dc@bootlin.com>
Date: Thu, 25 Sep 2025 14:37:37 +0200
From: Romain Gantois <romain.gantois@...tlin.com>
To: Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>, Jonathan Cameron <jic23@...nel.org>,
David Lechner <dlechner@...libre.com>,
Nuno Sá <nuno.sa@...log.com>,
Andy Shevchenko <andy@...nel.org>
Cc: Hans de Goede <hansg@...nel.org>,
Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
linux-iio@...r.kernel.org, Romain Gantois <romain.gantois@...tlin.com>
Subject: [PATCH v2 5/5] regulator: ltm8054: Support output current limit
control
The LTM8054 supports setting a fixed output current limit using a sense
resistor connected to a dedicated pin. This limit can then be lowered
dynamically by varying the voltage level of the CTL pin.
Support controlling the LTM8054's output current limit.
Signed-off-by: Romain Gantois <romain.gantois@...tlin.com>
---
drivers/regulator/Kconfig | 1 +
drivers/regulator/ltm8054-regulator.c | 113 +++++++++++++++++++++++++++++++++-
2 files changed, 112 insertions(+), 2 deletions(-)
diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
index c48b2af350974b3715a1ecf05dec656a92268294..e9ee6ed9fe3587c542223a6d6be78412e96797ee 100644
--- a/drivers/regulator/Kconfig
+++ b/drivers/regulator/Kconfig
@@ -579,6 +579,7 @@ config REGULATOR_LTC3676
config REGULATOR_LTM8054
tristate "LTM8054 Buck-Boost voltage regulator"
+ depends on IIO
help
This driver provides support for the Analog Devices LTM8054
Buck-Boost micromodule regulator. The LTM8054 has an adjustable
diff --git a/drivers/regulator/ltm8054-regulator.c b/drivers/regulator/ltm8054-regulator.c
index bc8cf98b5a3b5663481d148330de70a8165e5981..172ec32c5a9517c6fb38ded8095ffc8e1acf55f0 100644
--- a/drivers/regulator/ltm8054-regulator.c
+++ b/drivers/regulator/ltm8054-regulator.c
@@ -17,6 +17,8 @@
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/gpio/consumer.h>
+#include <linux/iio/consumer.h>
+#include <linux/minmax.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
@@ -26,10 +28,25 @@
#include <linux/regulator/driver.h>
#include <linux/regulator/of_regulator.h>
+#include <linux/units.h>
+
/* The LTM8054 regulates its FB pin to 1.2V */
#define LTM8054_FB_uV 1200000
+/* Threshold voltage between the Vout and Iout pins which triggers current
+ * limiting.
+ */
+#define LTM8054_VOUT_IOUT_MAX_uV 58000
+
+#define LTM8054_MAX_CTL_uV 1200000
+#define LTM8054_MIN_CTL_uV 50000
+
struct ltm8054_priv {
+ struct iio_channel *ctl_dac;
+
+ int min_uA;
+ int max_uA;
+
struct regulator_desc rdesc;
};
@@ -43,18 +60,103 @@ static int ltm8054_scale(unsigned int uV, u32 r1, u32 r2)
return uV + tmp;
}
-static const struct regulator_ops ltm8054_regulator_ops = { };
+static int ltm8054_set_current_limit(struct regulator_dev *rdev, int min_uA, int max_uA)
+{
+ struct ltm8054_priv *priv = rdev_get_drvdata(rdev);
+ u64 vdac_uV;
+
+ min_uA = clamp_t(int, min_uA, priv->min_uA, priv->max_uA);
+
+ /* adjusted current limit = Rsense current limit * CTL pin voltage / max CTL pin voltage */
+ vdac_uV = (u64)min_uA * LTM8054_MAX_CTL_uV;
+ do_div(vdac_uV, priv->max_uA);
+
+ dev_dbg(&rdev->dev,
+ "Setting current limit to %duA, CTL pin to %duV\n", min_uA, (int)vdac_uV);
+
+ /* Standard IIO voltage unit is mV, scale accordingly. */
+ return iio_write_channel_processed_scale(priv->ctl_dac, vdac_uV, 1000);
+}
+
+static int ltm8054_get_current_limit(struct regulator_dev *rdev)
+{
+ struct ltm8054_priv *priv = rdev_get_drvdata(rdev);
+ int ret, vdac_uv;
+ u64 uA;
+
+ ret = iio_read_channel_processed_scale(priv->ctl_dac, &vdac_uv, 1000);
+ if (ret < 0) {
+ dev_err(&rdev->dev, "failed to read CTL DAC voltage, err %d\n", ret);
+ return ret;
+ }
+
+ uA = (u64)vdac_uv * priv->max_uA;
+ do_div(uA, LTM8054_MAX_CTL_uV);
+
+ return uA;
+}
+
+static const struct regulator_ops ltm8054_regulator_ops = {
+ .set_current_limit = ltm8054_set_current_limit,
+ .get_current_limit = ltm8054_get_current_limit,
+};
+
+static int ltm8054_init_ctl_dac(struct platform_device *pdev, struct ltm8054_priv *priv)
+{
+ struct iio_channel *ctl_dac;
+ enum iio_chan_type type;
+ int ret;
+
+ ctl_dac = devm_iio_channel_get(&pdev->dev, "ctl");
+ if (IS_ERR(ctl_dac))
+ return PTR_ERR(ctl_dac);
+
+ ret = iio_get_channel_type(ctl_dac, &type);
+ if (ret)
+ return ret;
+
+ if (type != IIO_VOLTAGE)
+ return -EINVAL;
+
+ priv->ctl_dac = ctl_dac;
+
+ return 0;
+}
static int ltm8054_of_parse(struct device *dev, struct ltm8054_priv *priv,
struct regulator_config *config)
{
struct device_node *np = dev->of_node;
+ u32 rsense;
u32 r[2];
+ u64 tmp;
int ret;
config->of_node = np;
- ret = device_property_read_u32_array(dev, "lltc,fb-voltage-divider", r, ARRAY_SIZE(r));
+ ret = device_property_read_u32(dev, "adi,iout-rsense-micro-ohms", &rsense);
+ if (ret)
+ return ret;
+
+ if (rsense == 0)
+ return -EINVAL;
+
+ /* The maximum output current limit is the one set by the Rsense resistor */
+ tmp = (u64)LTM8054_VOUT_IOUT_MAX_uV * MICRO;
+ do_div(tmp, rsense);
+ priv->max_uA = tmp;
+
+ /*
+ * Applying a voltage below LTM8054_MAX_CTL_uV on the CTL pin reduces
+ * the output current limit. If this level drops below
+ * LTM8054_MIN_CTL_uV the regulator stops switching.
+ */
+
+ tmp = (u64)priv->max_uA * LTM8054_MIN_CTL_uV;
+ do_div(tmp, LTM8054_MAX_CTL_uV);
+ priv->min_uA = tmp;
+
+ ret = device_property_read_u32_array(dev, "lltc,fb-voltage-divider", r, 2);
if (ret)
return ret;
@@ -62,6 +164,9 @@ static int ltm8054_of_parse(struct device *dev, struct ltm8054_priv *priv,
priv->rdesc.min_uV = priv->rdesc.fixed_uV;
priv->rdesc.n_voltages = 1;
+ dev_dbg(dev, "max_uA: %d min_uA: %d fixed_uV: %d\n",
+ priv->max_uA, priv->min_uA, priv->rdesc.fixed_uV);
+
config->init_data = of_get_regulator_init_data(dev,
np,
&priv->rdesc);
@@ -99,6 +204,10 @@ static int ltm8054_probe(struct platform_device *pdev)
if (ret)
return dev_err_probe(dev, ret, "failed to parse device tree\n");
+ ret = ltm8054_init_ctl_dac(pdev, priv);
+ if (ret)
+ return dev_err_probe(dev, ret, "failed to initialize CTL DAC\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");
--
2.51.0
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