[PATCH 3/3] hwmon: (ctf2301) Add support for CTF2301

[Troy Mitchell <troy.mitchell@linux.dev>]

This commit introduces driver for the Sensylink CTF2301
system-level thermal management solution chip.

Currently, the driver does NOT support the Auto-Temp mode of the PWM
fan controller, which provides closed-loop automatic fan speed control
based on temperature.

Now this driver supports:
  - Reading local temperature.
  - Reading remote temperature.
  - Controlling the PWM fan output in Direct-DCY mode (direct duty cycle control).
  - Monitoring fan speed via the TACH input (RPM measurement).

Signed-off-by: Troy Mitchell <troy.mitchell@linux.dev>
---
 drivers/hwmon/Kconfig   |  11 ++
 drivers/hwmon/Makefile  |   1 +
 drivers/hwmon/ctf2301.c | 326 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 338 insertions(+)

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 9d28fcf7cd2a6f9e2f54694a717bd85ff4047b46..2120d891e549795c3f3416d08f71916af714f6b6 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -537,6 +537,17 @@ config SENSORS_CROS_EC
 	  This driver can also be built as a module. If so, the module
 	  will be called cros_ec_hwmon.
 
+config SENSORS_CTF2301
+	tristate "Sensylink CTF2301"
+	depends on I2C
+	select REGMAP
+	help
+	  If you say yes here you get support for Sensylink CTF2301
+	  sensor chip.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called ctf2301.
+
 config SENSORS_DRIVETEMP
 	tristate "Hard disk drives with temperature sensors"
 	depends on SCSI && ATA
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index cd8bc4752b4dbf015c6eb46157626f4e8f87dfae..12f2894ce8d5fbfd942409f6c43d78fbdece57b4 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -65,6 +65,7 @@ obj-$(CONFIG_SENSORS_CORETEMP)	+= coretemp.o
 obj-$(CONFIG_SENSORS_CORSAIR_CPRO) += corsair-cpro.o
 obj-$(CONFIG_SENSORS_CORSAIR_PSU) += corsair-psu.o
 obj-$(CONFIG_SENSORS_CROS_EC)	+= cros_ec_hwmon.o
+obj-$(CONFIG_SENSORS_CTF2301)	+= ctf2301.o
 obj-$(CONFIG_SENSORS_DA9052_ADC)+= da9052-hwmon.o
 obj-$(CONFIG_SENSORS_DA9055)+= da9055-hwmon.o
 obj-$(CONFIG_SENSORS_DELL_SMM)	+= dell-smm-hwmon.o
diff --git a/drivers/hwmon/ctf2301.c b/drivers/hwmon/ctf2301.c
new file mode 100644
index 0000000000000000000000000000000000000000..2fea4d195519ea34c1d4bf67456098b225d4d13c
--- /dev/null
+++ b/drivers/hwmon/ctf2301.c
@@ -0,0 +1,326 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Driver for CTF2301 system-level thermal management solution chip
+ * Datasheet: https://www.sensylink.com/upload/1/net.sensylink.portal/1689557281035.pdf
+ *
+ * Copyright (C) 2025 Troy Mitchell <troy.mitchell@linux.dev>
+ */
+
+#include <linux/hwmon.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+
+#define PWM_PARENT_CLOCK			360000
+
+#define CTF2301_LOCAL_TEMP_MSB			0x00
+#define CTF2301_RMT_TEMP_MSB			0x01
+#define CTF2301_ALERT_STATUS			0x02
+#define CTF2301_GLOBAL_CFG			0x03
+#define CTF2301_RMT_TEMP_LSB			0x10
+#define CTF2301_LOCAL_TEMP_LSB			0x15
+#define CTF2301_ALERT_MASK			0x16
+#define	CTF2301_ENHANCED_CFG			0x45
+#define CTF2301_TACH_COUNT_LSB			0x46
+#define CTF2301_TACH_COUNT_MSB			0x47
+#define CTF2301_PWM_AND_TACH_CFG		0x4a
+#define CTF2301_PWM_VALUE			0x4c
+#define CTF2301_PWM_FREQ			0x4d
+#define CTF2301_RMT_DIODE_TEMP_FILTER		0xbf
+
+/* remote diode fault alarm */
+#define ALERT_STATUS_RDFA			BIT(2)
+
+/* alert interrupts enable  */
+#define GLOBAL_CFG_ALERT_MASK			BIT(7)
+/* tach input enable  */
+#define GLOBAL_CFG_TACH_SEL			BIT(2)
+
+/* local high temperature alarm mask */
+#define ALERT_MASK_LHAM				BIT(6)
+/* remote high temperature alarm mask */
+#define ALERT_MASK_RHAM				BIT(4)
+/* remote low temperature alarm mask */
+#define ALERT_MASK_RLAM				BIT(3)
+/* remote t_crit alarm mask */
+#define ALERT_MASK_RCAM				BIT(1)
+/* tachometer alarm mask */
+#define ALERT_MASK_TCHAM			BIT(0)
+
+#define ALERT_MASK_ALL				(ALERT_MASK_LHAM | ALERT_MASK_RHAM | \
+						ALERT_MASK_RLAM | ALERT_MASK_RCAM | \
+						ALERT_MASK_TCHAM)
+
+/* enables signed format for high and t_crit setpoints */
+#define ENHANGCED_CFG_USF			BIT(3)
+
+/* PWM Programming enable */
+#define PWM_AND_TACH_CFG_PWPGM			BIT(5)
+
+#define PWM_DEFAULT_FREQ_CODE			0x17
+
+
+struct ctf2301 {
+	struct i2c_client *client;
+
+	struct regmap *regmap;
+
+	unsigned int pwm_freq_code;
+};
+
+static int ctf2301_read_temp(struct device *dev, u32 attr, int channel, long *val)
+{
+	int regval[2], raw, err, flag = 1, shift = 4, scale = 625;
+	struct ctf2301 *ctf2301 = dev_get_drvdata(dev);
+	unsigned int reg_msb = CTF2301_LOCAL_TEMP_MSB,
+		     reg_lsb = CTF2301_LOCAL_TEMP_LSB;
+
+	switch (attr) {
+	case hwmon_temp_input:
+		if (channel != 0 && channel != 1)
+			return -EOPNOTSUPP;
+
+		if (channel == 1) {
+			err = regmap_read(ctf2301->regmap, CTF2301_ALERT_STATUS, regval);
+			if (err)
+				return err;
+
+			if (regval[0] & ALERT_STATUS_RDFA)
+				return -ENODEV;
+
+			shift = 5;
+			scale = 1250;
+			reg_msb = CTF2301_RMT_TEMP_MSB;
+			reg_lsb = CTF2301_RMT_TEMP_LSB;
+		}
+
+		err = regmap_read(ctf2301->regmap, reg_msb, regval);
+		if (err)
+			return err;
+
+		err = regmap_read(ctf2301->regmap, reg_lsb, regval + 1);
+		if (err)
+			return err;
+
+		dev_err(dev, "local temp: lsb->0x%x, msb->0x%x", regval[1], regval[0]);
+
+		raw = (s16)((regval[0] << 8) | regval[1]);
+
+		raw >>= shift;
+
+		*val = raw * scale * flag;
+
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+static int ctf2301_read_fan(struct device *dev, u32 attr, long *val)
+{
+	struct ctf2301 *ctf2301 = dev_get_drvdata(dev);
+	int regval[2], err, speed;
+
+	switch (attr) {
+	case hwmon_fan_input:
+		err = regmap_read(ctf2301->regmap, CTF2301_TACH_COUNT_MSB, regval);
+		if (err)
+			return err;
+
+		err = regmap_read(ctf2301->regmap, CTF2301_TACH_COUNT_LSB, regval + 1);
+		if (err)
+			return err;
+
+		speed = (regval[0] << 8) | regval[1];
+
+		*val = (unsigned int)(1 * (5400000 / speed));
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+static int ctf2301_write_pwm(struct device *dev, u32 attr, long val)
+{
+	struct ctf2301 *ctf2301 = dev_get_drvdata(dev);
+	int err, map_val;
+
+	dev_err(dev, "write pwm: %d", attr);
+
+	switch (attr) {
+	case hwmon_pwm_input:
+		map_val = (val * ctf2301->pwm_freq_code * 2) / 255;
+		dev_err(dev, "val:%ld, map_val: %d", val, map_val);
+		err = regmap_write(ctf2301->regmap, CTF2301_PWM_VALUE, map_val);
+		if (err)
+			return err;
+		break;
+	case hwmon_pwm_freq:
+		ctf2301->pwm_freq_code = DIV_ROUND_UP(PWM_PARENT_CLOCK, val) / 2;
+		dev_err(dev, "pwm_freq_code: %d", ctf2301->pwm_freq_code);
+		err = regmap_write(ctf2301->regmap, CTF2301_PWM_FREQ, ctf2301->pwm_freq_code);
+		if (err)
+			return err;
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
+}
+
+static umode_t ctf2301_is_visible(const void *drvdata,
+				 enum hwmon_sensor_types type,
+				 u32 attr, int channel)
+{
+	switch (type) {
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_input:
+			return 0444;
+		default:
+			return 0;
+		}
+	case hwmon_fan:
+		switch (attr) {
+		case hwmon_fan_input:
+			return 0444;
+		default:
+			return 0;
+		}
+	case hwmon_pwm:
+		switch (attr) {
+		case hwmon_pwm_input:
+		case hwmon_pwm_freq:
+			return 0644;
+		default:
+			return 0;
+		}
+	default:
+		return 0;
+	}
+}
+
+static int ctf2301_read(struct device *dev, enum hwmon_sensor_types type,
+		       u32 attr, int channel, long *val)
+{
+	switch (type) {
+	case hwmon_temp:
+		return ctf2301_read_temp(dev, attr, channel, val);
+	case hwmon_fan:
+		return ctf2301_read_fan(dev, attr, val);
+	default:
+		return -EOPNOTSUPP;
+	}
+	return 0;
+}
+
+static int ctf2301_write(struct device *dev, enum hwmon_sensor_types type,
+			 u32 attr, int channel, long val)
+{
+	switch (type) {
+	case hwmon_pwm:
+		return ctf2301_write_pwm(dev, attr, val);
+	default:
+		return -EOPNOTSUPP;
+	}
+	return 0;
+}
+
+static const struct hwmon_channel_info * const ctf2301_info[] = {
+	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT, HWMON_T_INPUT),
+	HWMON_CHANNEL_INFO(pwm, HWMON_PWM_INPUT | HWMON_PWM_FREQ),
+	HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT),
+	NULL
+};
+
+static const struct hwmon_ops ctf2301_hwmon_ops = {
+	.is_visible = ctf2301_is_visible,
+	.read = ctf2301_read,
+	.write = ctf2301_write
+};
+
+static const struct hwmon_chip_info ctf2301_chip_info = {
+	.ops = &ctf2301_hwmon_ops,
+	.info = ctf2301_info,
+};
+
+static const struct regmap_config ctf2301_regmap_config = {
+	.max_register = CTF2301_RMT_DIODE_TEMP_FILTER,
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static int ctf2301_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct device *hwmon_dev;
+	struct ctf2301 *ctf2301;
+	int err;
+
+	ctf2301 = devm_kzalloc(dev, sizeof(*ctf2301), GFP_KERNEL);
+	if (!ctf2301)
+		return -ENOMEM;
+	ctf2301->client = client;
+
+	ctf2301->regmap = devm_regmap_init_i2c(client, &ctf2301_regmap_config);
+	if (IS_ERR(ctf2301->regmap))
+		return dev_err_probe(dev, PTR_ERR(ctf2301->regmap),
+				     "failed to allocate register map");
+
+	err = regmap_write(ctf2301->regmap, CTF2301_GLOBAL_CFG,
+			   GLOBAL_CFG_ALERT_MASK | GLOBAL_CFG_TACH_SEL);
+	if (err)
+		return dev_err_probe(dev, err,
+				     "failed to write CTF2301_GLOBAL_CFG register");
+
+	/*err = regmap_write(ctf2301->regmap, CTF2301_ALERT_MASK, ALERT_MASK_ALL);*/
+	/*if (err)*/
+		/*return dev_err_probe(dev, err,*/
+				     /*"failed to write CTF2301_ALERT_MASK");*/
+
+	err = regmap_write(ctf2301->regmap, CTF2301_ENHANCED_CFG, ENHANGCED_CFG_USF);
+	if (err)
+		return dev_err_probe(dev, err,
+				     "failed to write CTF2301_ENHANCED_CFG");
+
+	err = regmap_write(ctf2301->regmap, CTF2301_PWM_AND_TACH_CFG, PWM_AND_TACH_CFG_PWPGM);
+	if (err)
+		return dev_err_probe(dev, err,
+				     "failed to write CTF2301_PWM_AND_TACH_CFG");
+
+	ctf2301->pwm_freq_code = PWM_DEFAULT_FREQ_CODE;
+
+	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, ctf2301,
+							 &ctf2301_chip_info,
+							 NULL);
+	if (IS_ERR(hwmon_dev))
+		return dev_err_probe(dev, PTR_ERR(hwmon_dev),
+				     "failed to register hwmon device");
+
+	return 0;
+}
+
+static const struct of_device_id ctf2301_of_match[] = {
+	{ .compatible = "sensylink,ctf2301", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, ctf2301_of_match);
+
+static struct i2c_driver ctf2301_driver = {
+	.driver = {
+		.name	= "ctf2301",
+		.of_match_table = of_match_ptr(ctf2301_of_match),
+	},
+	.probe		= ctf2301_probe,
+};
+module_i2c_driver(ctf2301_driver);
+
+MODULE_AUTHOR("Troy Mitchell <troy.mitchell@linux.dev>");
+MODULE_DESCRIPTION("ctf2301 driver");
+MODULE_LICENSE("GPL");

-- 
2.51.0