hwmon: add SMARC-sAM67 support

Add a new driver for the Kontron SMARC-sAM67 board management
controller. It has two voltage sensors and one temperature sensor.

Signed-off-by: Michael Walle <mwalle@kernel.org>
Link: https://lore.kernel.org/r/20250912120745.2295115-7-mwalle@kernel.org
[groeck: Added sa67 to index.rst]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/index.rst

@@ -214,6 +214,7 @@ Hardware Monitoring Kernel Drivers
    q54sj108a2
    qnap-mcu-hwmon
    raspberrypi-hwmon
+   sa67
    sbrmi
    sbtsi_temp
    sch5627

Documentation/hwmon/sa67.rst

@@ -0,0 +1,41 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+Kernel driver sa67mcu
+=====================
+
+Supported chips:
+
+   * Kontron sa67mcu
+
+     Prefix: 'sa67mcu'
+
+     Datasheet: not available
+
+Authors: Michael Walle <mwalle@kernel.org>
+
+Description
+-----------
+
+The sa67mcu is a board management controller which also exposes a hardware
+monitoring controller.
+
+The controller has two voltage and one temperature sensor. The values are
+hold in two 8 bit registers to form one 16 bit value. Reading the lower byte
+will also capture the high byte to make the access atomic. The unit of the
+volatge sensors are 1mV and the unit of the temperature sensor is 0.1degC.
+
+Sysfs entries
+-------------
+
+The following attributes are supported.
+
+======================= ========================================================
+in0_label		"VDDIN"
+in0_input		Measured VDDIN voltage.
+
+in1_label		"VDD_RTC"
+in1_input		Measured VDD_RTC voltage.
+
+temp1_input		MCU temperature. Roughly the board temperature.
+======================= ========================================================
+

MAINTAINERS

@@ -23231,6 +23231,7 @@ F:	Documentation/devicetree/bindings/mfd/kontron,sl28cpld.yaml
 F:	Documentation/devicetree/bindings/pwm/kontron,sl28cpld-pwm.yaml
 F:	Documentation/devicetree/bindings/watchdog/kontron,sl28cpld-wdt.yaml
 F:	drivers/gpio/gpio-sl28cpld.c
+F:	drivers/hwmon/sa67mcu-hwmon.c
 F:	drivers/hwmon/sl28cpld-hwmon.c
 F:	drivers/irqchip/irq-sl28cpld.c
 F:	drivers/pwm/pwm-sl28cpld.c

drivers/hwmon/Kconfig

@@ -1905,6 +1905,16 @@ config SENSORS_RASPBERRYPI_HWMON
 	  This driver can also be built as a module. If so, the module
 	  will be called raspberrypi-hwmon.
 
+config SENSORS_SA67MCU
+	tristate "Kontron sa67mcu hardware monitoring driver"
+	depends on MFD_SL28CPLD || COMPILE_TEST
+	help
+	  If you say yes here you get support for the voltage and temperature
+	  monitor of the sa67 board management controller.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called sa67mcu-hwmon.
+
 config SENSORS_SL28CPLD
 	tristate "Kontron sl28cpld hardware monitoring driver"
 	depends on MFD_SL28CPLD || COMPILE_TEST

drivers/hwmon/Makefile

@@ -197,6 +197,7 @@ obj-$(CONFIG_SENSORS_PT5161L)	+= pt5161l.o
 obj-$(CONFIG_SENSORS_PWM_FAN)	+= pwm-fan.o
 obj-$(CONFIG_SENSORS_QNAP_MCU_HWMON)	+= qnap-mcu-hwmon.o
 obj-$(CONFIG_SENSORS_RASPBERRYPI_HWMON)	+= raspberrypi-hwmon.o
+obj-$(CONFIG_SENSORS_SA67MCU)	+= sa67mcu-hwmon.o
 obj-$(CONFIG_SENSORS_SBTSI)	+= sbtsi_temp.o
 obj-$(CONFIG_SENSORS_SBRMI)	+= sbrmi.o
 obj-$(CONFIG_SENSORS_SCH56XX_COMMON)+= sch56xx-common.o

drivers/hwmon/sa67mcu-hwmon.c

@@ -0,0 +1,161 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * sl67mcu hardware monitoring driver
+ *
+ * Copyright 2025 Kontron Europe GmbH
+ */
+
+#include <linux/bitfield.h>
+#include <linux/hwmon.h>
+#include <linux/kernel.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+
+#define SA67MCU_VOLTAGE(n)	(0x00 + ((n) * 2))
+#define SA67MCU_TEMP(n)		(0x04 + ((n) * 2))
+
+struct sa67mcu_hwmon {
+	struct regmap *regmap;
+	u32 offset;
+};
+
+static int sa67mcu_hwmon_read(struct device *dev,
+			      enum hwmon_sensor_types type, u32 attr,
+			      int channel, long *input)
+{
+	struct sa67mcu_hwmon *hwmon = dev_get_drvdata(dev);
+	unsigned int offset;
+	u8 reg[2];
+	int ret;
+
+	switch (type) {
+	case hwmon_in:
+		switch (attr) {
+		case hwmon_in_input:
+			offset = hwmon->offset + SA67MCU_VOLTAGE(channel);
+			break;
+		default:
+			return -EOPNOTSUPP;
+		}
+		break;
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_input:
+			offset = hwmon->offset + SA67MCU_TEMP(channel);
+			break;
+		default:
+			return -EOPNOTSUPP;
+		}
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	/* Reading the low byte will capture the value */
+	ret = regmap_bulk_read(hwmon->regmap, offset, reg, ARRAY_SIZE(reg));
+	if (ret)
+		return ret;
+
+	*input = reg[1] << 8 | reg[0];
+
+	/* Temperatures are s16 and in 0.1degC steps. */
+	if (type == hwmon_temp)
+		*input = sign_extend32(*input, 15) * 100;
+
+	return 0;
+}
+
+static const struct hwmon_channel_info * const sa67mcu_hwmon_info[] = {
+	HWMON_CHANNEL_INFO(in,
+			   HWMON_I_INPUT | HWMON_I_LABEL,
+			   HWMON_I_INPUT | HWMON_I_LABEL),
+	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
+	NULL
+};
+
+static const char *const sa67mcu_hwmon_in_labels[] = {
+	"VDDIN",
+	"VDD_RTC",
+};
+
+static int sa67mcu_hwmon_read_string(struct device *dev,
+				     enum hwmon_sensor_types type, u32 attr,
+				     int channel, const char **str)
+{
+	switch (type) {
+	case hwmon_in:
+		switch (attr) {
+		case hwmon_in_label:
+			*str = sa67mcu_hwmon_in_labels[channel];
+			return 0;
+		default:
+			return -EOPNOTSUPP;
+		}
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+static const struct hwmon_ops sa67mcu_hwmon_ops = {
+	.visible = 0444,
+	.read = sa67mcu_hwmon_read,
+	.read_string = sa67mcu_hwmon_read_string,
+};
+
+static const struct hwmon_chip_info sa67mcu_hwmon_chip_info = {
+	.ops = &sa67mcu_hwmon_ops,
+	.info = sa67mcu_hwmon_info,
+};
+
+static int sa67mcu_hwmon_probe(struct platform_device *pdev)
+{
+	struct sa67mcu_hwmon *hwmon;
+	struct device *hwmon_dev;
+	int ret;
+
+	if (!pdev->dev.parent)
+		return -ENODEV;
+
+	hwmon = devm_kzalloc(&pdev->dev, sizeof(*hwmon), GFP_KERNEL);
+	if (!hwmon)
+		return -ENOMEM;
+
+	hwmon->regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!hwmon->regmap)
+		return -ENODEV;
+
+	ret = device_property_read_u32(&pdev->dev, "reg", &hwmon->offset);
+	if (ret)
+		return -EINVAL;
+
+	hwmon_dev = devm_hwmon_device_register_with_info(&pdev->dev,
+							 "sa67mcu_hwmon", hwmon,
+							 &sa67mcu_hwmon_chip_info,
+							 NULL);
+	if (IS_ERR(hwmon_dev))
+		dev_err(&pdev->dev, "failed to register as hwmon device");
+
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct of_device_id sa67mcu_hwmon_of_match[] = {
+	{ .compatible = "kontron,sa67mcu-hwmon", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, sa67mcu_hwmon_of_match);
+
+static struct platform_driver sa67mcu_hwmon_driver = {
+	.probe = sa67mcu_hwmon_probe,
+	.driver = {
+		.name = "sa67mcu-hwmon",
+		.of_match_table = sa67mcu_hwmon_of_match,
+	},
+};
+module_platform_driver(sa67mcu_hwmon_driver);
+
+MODULE_DESCRIPTION("sa67mcu Hardware Monitoring Driver");
+MODULE_AUTHOR("Michael Walle <mwalle@kernel.org>");
+MODULE_LICENSE("GPL");