[v2,4/4] hwmon: add MP9941 driver

diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index 9d9d55b889f2..9ff8149d9a9d 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -169,6 +169,7 @@  Hardware Monitoring Kernel Drivers
    mp2993
    mp5023
    mp5990
+   mp9941
    mpq8785
    nct6683
    nct6775
diff --git a/Documentation/hwmon/mp9941.rst b/Documentation/hwmon/mp9941.rst
new file mode 100644
index 000000000000..1274fa20e256
--- /dev/null
+++ b/Documentation/hwmon/mp9941.rst
@@ -0,0 +1,92 @@ 
+.. SPDX-License-Identifier: GPL-2.0
+
+Kernel driver mp9941
+====================
+
+Supported chips:
+
+  * MPS mp9941
+
+    Prefix: 'mp9941'
+
+  * Datasheet
+    https://scnbwymvp-my.sharepoint.com/:f:/g/personal/admin_scnbwy_com/Eth4kX1_J1hMsaASHiOYL4QBHU5a75r-tRfLKbHnJFdKLQ?e=vxj3DF
+
+Author:
+
+	Noah Wang <noahwang.wang@outlook.com>
+
+Description
+-----------
+
+This driver implements support for Monolithic Power Systems, Inc. (MPS)
+MP9941 digital step-down converter.
+
+Device compliant with:
+
+- PMBus rev 1.3 interface.
+
+The driver exports the following attributes via the 'sysfs' files
+for input voltage:
+
+**in1_input**
+
+**in1_label**
+
+**in1_crit**
+
+**in1_crit_alarm**
+
+The driver provides the following attributes for output voltage:
+
+**in2_input**
+
+**in2_label**
+
+**in2_lcrit**
+
+**in2_lcrit_alarm**
+
+**in2_rated_max**
+
+**in2_rated_min**
+
+The driver provides the following attributes for input current:
+
+**curr1_input**
+
+**curr1_label**
+
+**curr1_max**
+
+**curr1_max_alarm**
+
+The driver provides the following attributes for output current:
+
+**curr2_input**
+
+**curr2_label**
+
+The driver provides the following attributes for input power:
+
+**power1_input**
+
+**power1_label**
+
+The driver provides the following attributes for output power:
+
+**power2_input**
+
+**power2_label**
+
+The driver provides the following attributes for temperature:
+
+**temp1_input**
+
+**temp1_crit**
+
+**temp1_crit_alarm**
+
+**temp1_max**
+
+**temp1_max_alarm**
diff --git a/MAINTAINERS b/MAINTAINERS
index 4fdd787b1401..14dfbba64a54 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15263,6 +15263,13 @@  S:	Maintained
 F:	Documentation/hwmon/mp2993.rst
 F:	drivers/hwmon/pmbus/mp2993.c
 
+MPS MP9941 DRIVER
+M:	Noah Wang <noahwang.wang@outlook.com>
+L:	linux-hwmon@vger.kernel.org
+S:	Maintained
+F:	Documentation/hwmon/mp9941.rst
+F:	drivers/hwmon/pmbus/mp9941.c
+
 MR800 AVERMEDIA USB FM RADIO DRIVER
 M:	Alexey Klimov <klimov.linux@gmail.com>
 L:	linux-media@vger.kernel.org
diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
index d875d31ce84c..7d32cfc19820 100644
--- a/drivers/hwmon/pmbus/Kconfig
+++ b/drivers/hwmon/pmbus/Kconfig
@@ -380,6 +380,15 @@  config SENSORS_MP5990
 	  This driver can also be built as a module. If so, the module will
 	  be called mp5990.
 
+config SENSORS_MP9941
+	tristate "MPS MP9941"
+	help
+	  If you say yes here you get hardware monitoring support for MPS
+	  MP9941.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called mp9941.
+
 config SENSORS_MPQ7932_REGULATOR
 	bool "Regulator support for MPQ7932"
 	depends on SENSORS_MPQ7932 && REGULATOR
diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
index 312d3f0c0540..6c7177fde355 100644
--- a/drivers/hwmon/pmbus/Makefile
+++ b/drivers/hwmon/pmbus/Makefile
@@ -40,6 +40,7 @@  obj-$(CONFIG_SENSORS_MP2975)	+= mp2975.o
 obj-$(CONFIG_SENSORS_MP2993)	+= mp2993.o
 obj-$(CONFIG_SENSORS_MP5023)	+= mp5023.o
 obj-$(CONFIG_SENSORS_MP5990)	+= mp5990.o
+obj-$(CONFIG_SENSORS_MP9941)	+= mp9941.o
 obj-$(CONFIG_SENSORS_MPQ7932)	+= mpq7932.o
 obj-$(CONFIG_SENSORS_MPQ8785)	+= mpq8785.o
 obj-$(CONFIG_SENSORS_PLI1209BC)	+= pli1209bc.o
diff --git a/drivers/hwmon/pmbus/mp9941.c b/drivers/hwmon/pmbus/mp9941.c
new file mode 100644
index 000000000000..b7b0eda5b552
--- /dev/null
+++ b/drivers/hwmon/pmbus/mp9941.c
@@ -0,0 +1,317 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Hardware monitoring driver for MPS Multi-phase Digital VR Controllers(MP9941)
+ */
+
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include "pmbus.h"
+
+/*
+ * Vender specific registers. The MFR_ICC_MAX(0x02) is used to
+ * config the iin scale. The MFR_RESO_SET(0xC7) is used to
+ * config the vout format. The MFR_VR_MULTI_CONFIG_R1(0x0D) is
+ * used to identify the vout vid step.
+ */
+#define MFR_ICC_MAX	0x02
+#define MFR_RESO_SET	0xC7
+#define MFR_VR_MULTI_CONFIG_R1	0x0D
+
+#define MP9941_VIN_LIMIT_UINT	1
+#define MP9941_VIN_LIMIT_DIV	8
+#define MP9941_READ_VIN_UINT	1
+#define MP9941_READ_VIN_DIV	32
+
+#define MP9941_PAGE_NUM	1
+
+#define MP9941_RAIL1_FUNC	(PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT | \
+							PMBUS_HAVE_IOUT | PMBUS_HAVE_POUT | \
+							PMBUS_HAVE_TEMP | PMBUS_HAVE_PIN | \
+							PMBUS_HAVE_IIN | \
+							PMBUS_HAVE_STATUS_VOUT | \
+							PMBUS_HAVE_STATUS_IOUT | \
+							PMBUS_HAVE_STATUS_TEMP | \
+							PMBUS_HAVE_STATUS_INPUT)
+
+struct mp9941_data {
+	struct pmbus_driver_info info;
+	int vid_resolution;
+};
+
+#define to_mp9941_data(x) container_of(x, struct mp9941_data, info)
+
+static int mp9941_set_vout_format(struct i2c_client *client)
+{
+	int ret;
+
+	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 0);
+	if (ret < 0)
+		return ret;
+
+	ret = i2c_smbus_read_word_data(client, MFR_RESO_SET);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * page = 0, MFR_RESO_SET[7:6] defines the vout format
+	 * 2'b11 set the vout format as direct
+	 */
+	ret = (ret & ~GENMASK(7, 6)) | FIELD_PREP(GENMASK(7, 6), 3);
+
+	return i2c_smbus_write_word_data(client, MFR_RESO_SET, ret);
+}
+
+static int
+mp9941_identify_vid_resolution(struct i2c_client *client, struct pmbus_driver_info *info)
+{
+	struct mp9941_data *data = to_mp9941_data(info);
+	int ret;
+
+	/*
+	 * page = 2, MFR_VR_MULTI_CONFIG_R1[4:4] defines rail1 vid step value
+	 * 1'b0 represents the vid step value is 10mV
+	 * 1'b1 represents the vid step value is 5mV
+	 */
+	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 2);
+	if (ret < 0)
+		return ret;
+
+	ret = i2c_smbus_read_word_data(client, MFR_VR_MULTI_CONFIG_R1);
+	if (ret < 0)
+		return ret;
+
+	if (FIELD_GET(GENMASK(4, 4), ret))
+		data->vid_resolution = 5;
+	else
+		data->vid_resolution = 10;
+
+	return 0;
+}
+
+static int mp9941_identify_iin_scale(struct i2c_client *client)
+{
+	int ret;
+
+	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 0);
+	if (ret < 0)
+		return ret;
+
+	ret = i2c_smbus_read_word_data(client, MFR_RESO_SET);
+	if (ret < 0)
+		return ret;
+
+	ret = (ret & ~GENMASK(3, 2)) | FIELD_PREP(GENMASK(3, 2), 0);
+
+	ret = i2c_smbus_write_word_data(client, MFR_RESO_SET, ret);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * page = 2, MFR_ICC_MAX[15:13] defines the iin scale
+	 * 3'b000 set the iout scale as 0.5A/Lsb
+	 */
+	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 2);
+	if (ret < 0)
+		return ret;
+
+	ret = i2c_smbus_read_word_data(client, MFR_ICC_MAX);
+	if (ret < 0)
+		return ret;
+
+	ret = (ret & ~GENMASK(15, 13)) | FIELD_PREP(GENMASK(15, 13), 0);
+
+	return i2c_smbus_write_word_data(client, MFR_ICC_MAX, ret);
+}
+
+static int mp9941_identify(struct i2c_client *client, struct pmbus_driver_info *info)
+{
+	int ret;
+
+	ret = mp9941_identify_iin_scale(client);
+	if (ret < 0)
+		return ret;
+
+	ret = mp9941_identify_vid_resolution(client, info);
+	if (ret < 0)
+		return ret;
+
+	return mp9941_set_vout_format(client);
+}
+
+static int mp9941_read_word_data(struct i2c_client *client, int page, int phase,
+				 int reg)
+{
+	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
+	struct mp9941_data *data = to_mp9941_data(info);
+	int ret;
+
+	switch (reg) {
+	case PMBUS_READ_VIN:
+		/* The MP9941 vin scale is (1/32V)/Lsb */
+		ret = pmbus_read_word_data(client, page, phase, reg);
+		if (ret < 0)
+			return ret;
+
+		ret = DIV_ROUND_CLOSEST((ret & GENMASK(9, 0)) * MP9941_READ_VIN_UINT,
+					MP9941_READ_VIN_DIV);
+		break;
+	case PMBUS_READ_IIN:
+		ret = pmbus_read_word_data(client, page, phase, reg);
+		if (ret < 0)
+			return ret;
+
+		ret = ret & GENMASK(10, 0);
+		break;
+	case PMBUS_VIN_OV_FAULT_LIMIT:
+		/* The MP9941 vin ov limit scale is (1/8V)/Lsb */
+		ret = pmbus_read_word_data(client, page, phase, reg);
+		if (ret < 0)
+			return ret;
+
+		ret = DIV_ROUND_CLOSEST((ret & GENMASK(7, 0)) * MP9941_VIN_LIMIT_UINT,
+					MP9941_VIN_LIMIT_DIV);
+		break;
+	case PMBUS_IIN_OC_WARN_LIMIT:
+		ret = pmbus_read_word_data(client, page, phase, reg);
+		if (ret < 0)
+			return ret;
+
+		ret = ret & GENMASK(7, 0);
+		break;
+	case PMBUS_VOUT_UV_FAULT_LIMIT:
+	case PMBUS_MFR_VOUT_MIN:
+	case PMBUS_MFR_VOUT_MAX:
+		/*
+		 * The vout scale is set to 1mV/Lsb(using r/m/b scale).
+		 * But the vout uv limit and vout max/min scale is 1VID/Lsb,
+		 * so the vout uv limit and vout max/min value should be
+		 * multiplied by vid resolution.
+		 */
+		ret = pmbus_read_word_data(client, page, phase, reg);
+		if (ret < 0)
+			return ret;
+
+		ret = ret * data->vid_resolution;
+		break;
+	case PMBUS_READ_IOUT:
+	case PMBUS_READ_POUT:
+	case PMBUS_READ_TEMPERATURE_1:
+	case PMBUS_READ_VOUT:
+	case PMBUS_READ_PIN:
+	case PMBUS_OT_FAULT_LIMIT:
+	case PMBUS_OT_WARN_LIMIT:
+		ret = -ENODATA;
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	return ret;
+}
+
+static int mp9941_write_word_data(struct i2c_client *client, int page, int reg,
+				  u16 word)
+{
+	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
+	struct mp9941_data *data = to_mp9941_data(info);
+	int ret;
+
+	switch (reg) {
+	case PMBUS_VIN_OV_FAULT_LIMIT:
+		/* The MP9941 vin ov limit scale is (1/8V)/Lsb */
+		ret = pmbus_write_word_data(client, page, reg,
+					    DIV_ROUND_CLOSEST(word * MP9941_VIN_LIMIT_DIV,
+							      MP9941_VIN_LIMIT_UINT));
+		break;
+	case PMBUS_VOUT_UV_FAULT_LIMIT:
+	case PMBUS_MFR_VOUT_MIN:
+	case PMBUS_MFR_VOUT_MAX:
+		ret = pmbus_write_word_data(client, page, reg,
+					    DIV_ROUND_CLOSEST(word, data->vid_resolution));
+		break;
+	case PMBUS_IIN_OC_WARN_LIMIT:
+	case PMBUS_OT_FAULT_LIMIT:
+	case PMBUS_OT_WARN_LIMIT:
+		ret = -ENODATA;
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	return ret;
+}
+
+static const struct pmbus_driver_info mp9941_info = {
+	.pages = MP9941_PAGE_NUM,
+	.format[PSC_VOLTAGE_IN] = direct,
+	.format[PSC_CURRENT_IN] = direct,
+	.format[PSC_CURRENT_OUT] = linear,
+	.format[PSC_POWER] = linear,
+	.format[PSC_TEMPERATURE] = direct,
+	.format[PSC_VOLTAGE_OUT] = direct,
+
+	.m[PSC_TEMPERATURE] = 1,
+	.R[PSC_TEMPERATURE] = 0,
+	.b[PSC_TEMPERATURE] = 0,
+
+	.m[PSC_VOLTAGE_IN] = 1,
+	.R[PSC_VOLTAGE_IN] = 0,
+	.b[PSC_VOLTAGE_IN] = 0,
+
+	.m[PSC_CURRENT_IN] = 2,
+	.R[PSC_CURRENT_IN] = 0,
+	.b[PSC_CURRENT_IN] = 0,
+
+	.m[PSC_VOLTAGE_OUT] = 1,
+	.R[PSC_VOLTAGE_OUT] = 3,
+	.b[PSC_VOLTAGE_OUT] = 0,
+
+	.func[0] = MP9941_RAIL1_FUNC,
+	.read_word_data = mp9941_read_word_data,
+	.write_word_data = mp9941_write_word_data,
+	.identify = mp9941_identify,
+};
+
+static int mp9941_probe(struct i2c_client *client)
+{
+	struct mp9941_data *data;
+
+	data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	memcpy(&data->info, &mp9941_info, sizeof(mp9941_info));
+
+	return pmbus_do_probe(client, &data->info);
+}
+
+static const struct i2c_device_id mp9941_id[] = {
+	{"mp9941", 0},
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, mp9941_id);
+
+static const struct of_device_id __maybe_unused mp9941_of_match[] = {
+	{.compatible = "mps,mp9941"},
+	{}
+};
+MODULE_DEVICE_TABLE(of, mp9941_of_match);
+
+static struct i2c_driver mp9941_driver = {
+	.driver = {
+		.name = "mp9941",
+		.of_match_table = mp9941_of_match,
+	},
+	.probe = mp9941_probe,
+	.id_table = mp9941_id,
+};
+
+module_i2c_driver(mp9941_driver);
+
+MODULE_AUTHOR("Noah Wang <noahwang.wang@outlook.com>");
+MODULE_DESCRIPTION("PMBus driver for MPS MP9941");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS(PMBUS);