From: Nuno Sá <nuno.sa@xxxxxxxxxx>
The LTC4283 is a negative voltage hot swap controller that drives an
external N-channel MOSFET to allow a board to be safely inserted and
removed from a live backplane.
Main usage is as an Hardware Monitoring device. However, it has up to 8
pins that can be configured and used as GPIOs and hence, the device can
also be a GPIO controller (and so being added as MFD device).
Signed-off-by: Nuno Sá <nuno.sa@xxxxxxxxxx>
---
MAINTAINERS | 2 +
drivers/mfd/Kconfig | 11 ++++
drivers/mfd/Makefile | 1 +
drivers/mfd/ltc4283.c | 140 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/mfd/ltc4283.h | 33 +++++++++++
5 files changed, 187 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index 413bb77d5eebe2b51aa9c3af86e7cfd5ab142044..b5f4f1c41c64b738d57c1fb5552a60b4c6b9985c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14506,6 +14506,8 @@ L: linux-hwmon@xxxxxxxxxxxxxxx
L: linux-gpio@xxxxxxxxxxxxxxx
S: Supported
F: Documentation/devicetree/bindings/mfd/adi,ltc4283.yaml
+F: drivers/mfd/ltc4283.c
+F: include/linux/mfd/ltc4283.h
LTC4286 HARDWARE MONITOR DRIVER
M: Delphine CC Chiu <Delphine_CC_Chiu@xxxxxxxxxx>
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 425c5fba6cb1e7848dcea05bd77c729a71d48e2c..ec3e02d40fd17a0bba29e3157723055feedebd11 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -900,6 +900,17 @@ config MFD_MAX14577
additional drivers must be enabled in order to use the functionality
of the device.
+config MFD_LTC4283
+ tristate "LTC4283 Hot Swap Controller"
+ depends on I2C
+ select MFD_CORE
+ select REGMAP_I2C
+ help
+ This enables support for the LTC4283 Negative Voltage Hot Swap
+ Controller. This driver provides common support for accessing the
+ device; additional drivers must be enabled in order to use the
+ functionality of the device.
+
config MFD_MAX77541
tristate "Analog Devices MAX77541/77540 PMIC Support"
depends on I2C=y
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index f7bdedd5a66d16bf8ccee0da1236a441e6f085b0..4a3bcd30ab7e12aed4bc5e48294500c77cb61aa7 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -23,6 +23,7 @@ obj-$(CONFIG_MFD_EXYNOS_LPASS) += exynos-lpass.o
obj-$(CONFIG_MFD_GATEWORKS_GSC) += gateworks-gsc.o
obj-$(CONFIG_MFD_MACSMC) += macsmc.o
+obj-$(CONFIG_MFD_LTC4283) += ltc4283.o
obj-$(CONFIG_MFD_TI_LP873X) += lp873x.o
obj-$(CONFIG_MFD_TI_LP87565) += lp87565.o
obj-$(CONFIG_MFD_TI_AM335X_TSCADC) += ti_am335x_tscadc.o
diff --git a/drivers/mfd/ltc4283.c b/drivers/mfd/ltc4283.c
new file mode 100644
index 0000000000000000000000000000000000000000..a45c01278f884630984790c922c057c4f2db9c82
--- /dev/null
+++ b/drivers/mfd/ltc4283.c
@@ -0,0 +1,140 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Analog Devices LTC4283 I2C Negative Voltage Hot Swap Controller
+ *
+ * Copyright 2025 Analog Devices Inc.
+ */
+#include <linux/bitmap.h>
+#include <linux/bitops.h>
+#include <linux/device.h>
+#include <linux/i2c.h>
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/regmap.h>
+#include <linux/property.h>
+
+#include <linux/mfd/ltc4283.h>
+
+static const struct mfd_cell ltc4283_cells[] = {
+ MFD_CELL_OF("ltc4283-hwmon", NULL, NULL, 0, 0, "adi,ltc4283-hwmon"),
+ MFD_CELL_OF("ltc4283-gpio", NULL, NULL, 0, 0, "adi,ltc4283-gpio"),
+};
+
+static bool ltc4283_writable_reg(struct device *dev, unsigned int reg)
+{
+ switch (reg) {
+ case 0x00 ... 0x03:
+ return false;
+ case 0x3c:
+ return false;
+ case 0x86 ... 0x8f:
+ return false;
+ case 0x91 ... 0xa1:
+ return false;
+ case 0xa3:
+ return false;
+ case 0xac:
+ return false;
+ case 0xf1 ... 0xff:
+ return false;
+ default:
+ return true;
+ }
+}
+
+static const struct regmap_config ltc4283_regmap_config = {
+ .reg_bits = 8,
+ .val_bits = 8,
+ .max_register = 0xff,
+ .writeable_reg = ltc4283_writable_reg,
+};
+
+static int ltc4283_get_gpio_pins(struct i2c_client *client, u32 *n_cells)
+{
+ struct device *dev = &client->dev;
+ u32 pins[LTC4283_GPIO_MAX], pin;
+ unsigned long *gpio_mask;
+ int n_pins, ret;
+
+ /*
+ * The device has up to 8 pins that can be configured either as GPIOS or
+ * for monitoring purposes. Both gpio and hwmon devices need to have
+ * this information in order to do proper validations and
+ * configurations. Hence, this property needs to be in the top level
+ * device.
+ */
+ n_pins = device_property_count_u32(dev, "adi,gpio-pins");
+ if (n_pins < 0)
+ return 0;
+ if (n_pins >= LTC4283_GPIO_MAX)
+ return dev_err_probe(dev, -EINVAL, "Too many GPIO pins specified (%d), max is %d\n",
+ n_pins, LTC4283_GPIO_MAX);
+
+ ret = device_property_read_u32_array(dev, "adi,gpio-pins", pins, n_pins);
+ if (ret)
+ return dev_err_probe(dev, ret, "Failed to read GPIO pins\n");
+
+ gpio_mask = devm_bitmap_zalloc(dev, LTC4283_GPIO_MAX, GFP_KERNEL);
+ if (!gpio_mask)
+ return -ENOMEM;
+
+ for (pin = 0; pin < n_pins; pin++) {
+ if (pins[pin] >= LTC4283_GPIO_MAX)
+ return dev_err_probe(dev, -EINVAL,
+ "Invalid GPIO pin specified (%u), max is %d\n",
+ pins[pin], LTC4283_GPIO_MAX);
+
+ __set_bit(pins[pin], gpio_mask);
+ }
+
+ /* Add the GPIO cell */
+ *n_cells += 1;
+ i2c_set_clientdata(client, gpio_mask);
+
+ return 0;
+}
+
+static int ltc4283_probe(struct i2c_client *client)
+{
+ u32 n_cells = ARRAY_SIZE(ltc4283_cells) - 1;
+ struct regmap *regmap;
+ int ret;
+
+ regmap = devm_regmap_init_i2c(client, <c4283_regmap_config);
+ if (IS_ERR(regmap))
+ return PTR_ERR(regmap);
+
+ ret = ltc4283_get_gpio_pins(client, &n_cells);
+ if (ret)
+ return ret;
+
+ return devm_mfd_add_devices(&client->dev, PLATFORM_DEVID_AUTO,
+ ltc4283_cells, n_cells, NULL, 0, NULL);
+}
+
+static const struct of_device_id ltc4283_of_match[] = {
+ { .compatible = "adi,ltc4283" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, ltc4283_of_match);
+
+static const struct i2c_device_id ltc4283_i2c_id[] = {
+ { "ltc4283" },
+ { }
+};
+MODULE_DEVICE_TABLE(i2c, ltc4283_i2c_id);
+
+static struct i2c_driver ltc4283_driver = {
+ .driver = {
+ .name = "ltc4283",
+ .of_match_table = ltc4283_of_match,
+ },
+ .probe = ltc4283_probe,
+ .id_table = ltc4283_i2c_id,
+};
+module_i2c_driver(ltc4283_driver);
+
+MODULE_AUTHOR("Nuno Sá <nuno.sa@xxxxxxxxxx>");
+MODULE_DESCRIPTION("LTC4283 MFD I2C driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/mfd/ltc4283.h b/include/linux/mfd/ltc4283.h
new file mode 100644
index 0000000000000000000000000000000000000000..153594009c07b296ce5743e5e817e96464d81cb3
--- /dev/null
+++ b/include/linux/mfd/ltc4283.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Analog Devices LTC4283 I2C Negative Voltage Hot Swap Controller
+ *
+ * Copyright 2025 Analog Devices Inc.
+ */
+
+#ifndef __MFD_LTC4283_H_
+#define __MFD_LTC4283_H_
+
+#include <linux/bitops.h>
+#include <linux/bits.h>
+
+/*
+ * We can have up to 8 gpios. 4 PGIOs and 4 ADIOs. PGIOs start at index 4 in the
+ * gpios mask.
+ */
+#define LTC4283_PGIOX_START_NR 4
+
+#define LTC4283_PGIO_CONFIG 0x10
+#define LTC4283_PGIO_CFG_MASK(pin) \
+ GENMASK(((pin) - LTC4283_PGIOX_START_NR) * 2 + 1, (((pin) - LTC4283_PGIOX_START_NR) * 2))
+#define LTC4283_PGIO_CONFIG_2 0x11
+#define LTC4283_ADC_MASK GENMASK(2, 0)
+#define LTC4283_PGIO_OUT_MASK(pin) BIT(4 + (pin))
+
+#define LTC4283_GPIO_MAX 8
+
+/* Non-constant mask variant of FIELD_GET() and FIELD_PREP() */
+#define field_get(_mask, _reg) (((_reg) & (_mask)) >> (ffs(_mask) - 1))
+#define field_prep(_mask, _val) (((_val) << (ffs(_mask) - 1)) & (_mask))
+
+#endif
--
2.50.1
