hwmon: (pmbus) Add support for MPS Multi-phase mp2975 controller

Add support for mp295 device from Monolithic Power Systems, Inc. (MPS)
vendor. This is a dual-loop, digital, multi-phase controller.
This device:
- Supports two power rail.
- Provides 8 pulse-width modulations (PWMs), and can be configured up
  to 8-phase operation for rail 1 and up to 4-phase operation for rail
  2.
- Supports two pages 0 and 1 for telemetry and also pages 2 and 3 for
  configuration.
- Can configured VOUT readout in direct or VID format and allows
  setting of different formats on rails 1 and 2. For VID the following
  protocols are available: VR13 mode with 5-mV DAC; VR13 mode with
  10-mV DAC, IMVP9 mode with 5-mV DAC.

Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>
Link: https://lore.kernel.org/r/20200926204957.10268-2-vadimp@nvidia.com
[groeck: Cleaned up a couple of error returns; fixed up API changes]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

4 files changed, 895 insertions, 0 deletions

diff --git a/Documentation/hwmon/mp2975.rst b/Documentation/hwmon/mp2975.rst
new file mode 100644
index 000000000000..5b0609c62f48
--- /dev/null
+++ b/Documentation/hwmon/mp2975.rst
@@ -0,0 +1,116 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Kernel driver mp2975
+====================
+
+Supported chips:
+
+  * MPS MP12254
+
+    Prefix: 'mp2975'
+
+Author:
+
+	Vadim Pasternak <vadimp@nvidia.com>
+
+Description
+-----------
+
+This driver implements support for Monolithic Power Systems, Inc. (MPS)
+vendor dual-loop, digital, multi-phase controller MP2975.
+
+This device:
+- Supports up to two power rail.
+- Provides 8 pulse-width modulations (PWMs), and can be configured up
+  to 8-phase operation for rail 1 and up to 4-phase operation for rail
+  2.
+- Supports two pages 0 and 1 for telemetry and also pages 2 and 3 for
+  configuration.
+- Can configured VOUT readout in direct or VID format and allows
+  setting of different formats on rails 1 and 2. For VID the following
+  protocols are available: VR13 mode with 5-mV DAC; VR13 mode with
+  10-mV DAC, IMVP9 mode with 5-mV DAC.
+
+Device supports:
+- SVID interface.
+- AVSBus interface.
+
+Device complaint with:
+- PMBus rev 1.3 interface.
+
+Device supports direct format for reading output current, output voltage,
+input and output power and temperature.
+Device supports linear format for reading input voltage and input power.
+Device supports VID and direct formats for reading output voltage.
+The below VID modes are supported: VR12, VR13, IMVP9.
+
+The driver provides the next attributes for the current:
+- for current in: input, maximum alarm;
+- for current out input, maximum alarm and highest values;
+- for phase current: input and label.
+attributes.
+The driver exports the following attributes via the 'sysfs' files, where
+- 'n' is number of telemetry pages (from 1 to 2);
+- 'k' is number of configured phases (from 1 to 8);
+- indexes 1, 1*n for "iin";
+- indexes n+1, n+2 for "iout";
+- indexes 2*n+1 ... 2*n + k for phases.
+
+**curr[1-{2n}]_alarm**
+
+**curr[{n+1}-{n+2}]_highest**
+
+**curr[1-{2n+k}]_input**
+
+**curr[1-{2n+k}]_label**
+
+The driver provides the next attributes for the voltage:
+- for voltage in: input, high critical threshold, high critical alarm, all only
+  from page 0;
+- for voltage out: input, low and high critical thresholds, low and high
+  critical alarms, from pages 0 and 1;
+The driver exports the following attributes via the 'sysfs' files, where
+- 'n' is number of telemetry pages (from 1 to 2);
+- indexes 1 for "iin";
+- indexes n+1, n+2 for "vout";
+
+**in[1-{2n+1}]_crit**
+
+**in[1-{2n+1}]_crit_alarm**
+
+**in[1-{2n+1}]_input**
+
+**in[1-{2n+1}]_label**
+
+**in[2-{n+1}]_lcrit**
+
+**in[2-{n+1}1_lcrit_alarm**
+
+The driver provides the next attributes for the power:
+- for power in alarm and input.
+- for power out: highest and input.
+The driver exports the following attributes via the 'sysfs' files, where
+- 'n' is number of telemetry pages (from 1 to 2);
+- indexes 1 for "pin";
+- indexes n+1, n+2 for "pout";
+
+**power1_alarm**
+
+**power[2-{n+1}]_highest**
+
+**power[1-{2n+1}]_input**
+
+**power[1-{2n+1}]_label**
+
+The driver provides the next attributes for the temperature (only from page 0):
+
+
+**temp1_crit**
+
+**temp1_crit_alarm**
+
+**temp1_input**
+
+**temp1_max**
+
+**temp1_max_alarm**
diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
index db90e0018948..a25faf69fce3 100644
--- a/drivers/hwmon/pmbus/Kconfig
+++ b/drivers/hwmon/pmbus/Kconfig
@@ -211,6 +211,15 @@ config SENSORS_MAX8688
 	  This driver can also be built as a module. If so, the module will
 	  be called max8688.
 
+config SENSORS_MP2975
+	tristate "MPS MP2975"
+	help
+	  If you say yes here you get hardware monitoring support for MPS
+	  MP2975 Dual Loop Digital Multi-Phase Controller.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called mp2975.
+
 config SENSORS_PXE1610
 	tristate "Infineon PXE1610"
 	help
diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
index da41d22be1c9..4c97ad0bd791 100644
--- a/drivers/hwmon/pmbus/Makefile
+++ b/drivers/hwmon/pmbus/Makefile
@@ -24,6 +24,7 @@ obj-$(CONFIG_SENSORS_MAX20751)	+= max20751.o
 obj-$(CONFIG_SENSORS_MAX31785)	+= max31785.o
 obj-$(CONFIG_SENSORS_MAX34440)	+= max34440.o
 obj-$(CONFIG_SENSORS_MAX8688)	+= max8688.o
+obj-$(CONFIG_SENSORS_MP2975)	+= mp2975.o
 obj-$(CONFIG_SENSORS_PXE1610)	+= pxe1610.o
 obj-$(CONFIG_SENSORS_TPS40422)	+= tps40422.o
 obj-$(CONFIG_SENSORS_TPS53679)	+= tps53679.o
diff --git a/drivers/hwmon/pmbus/mp2975.c b/drivers/hwmon/pmbus/mp2975.c
new file mode 100644
index 000000000000..1c3e2a9453b1
--- /dev/null
+++ b/drivers/hwmon/pmbus/mp2975.c
@@ -0,0 +1,769 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Hardware monitoring driver for MPS Multi-phase Digital VR Controllers
+ *
+ * Copyright (C) 2020 Nvidia Technologies Ltd.
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include "pmbus.h"
+
+/* Vendor specific registers. */
+#define MP2975_MFR_APS_HYS_R2		0x0d
+#define MP2975_MFR_SLOPE_TRIM3		0x1d
+#define MP2975_MFR_VR_MULTI_CONFIG_R1	0x0d
+#define MP2975_MFR_VR_MULTI_CONFIG_R2	0x1d
+#define MP2975_MFR_APS_DECAY_ADV	0x56
+#define MP2975_MFR_DC_LOOP_CTRL		0x59
+#define MP2975_MFR_OCP_UCP_PHASE_SET	0x65
+#define MP2975_MFR_VR_CONFIG1		0x68
+#define MP2975_MFR_READ_CS1_2		0x82
+#define MP2975_MFR_READ_CS3_4		0x83
+#define MP2975_MFR_READ_CS5_6		0x84
+#define MP2975_MFR_READ_CS7_8		0x85
+#define MP2975_MFR_READ_CS9_10		0x86
+#define MP2975_MFR_READ_CS11_12		0x87
+#define MP2975_MFR_READ_IOUT_PK		0x90
+#define MP2975_MFR_READ_POUT_PK		0x91
+#define MP2975_MFR_READ_VREF_R1		0xa1
+#define MP2975_MFR_READ_VREF_R2		0xa3
+#define MP2975_MFR_OVP_TH_SET		0xe5
+#define MP2975_MFR_UVP_SET		0xe6
+
+#define MP2975_VOUT_FORMAT		BIT(15)
+#define MP2975_VID_STEP_SEL_R1		BIT(4)
+#define MP2975_IMVP9_EN_R1		BIT(13)
+#define MP2975_VID_STEP_SEL_R2		BIT(3)
+#define MP2975_IMVP9_EN_R2		BIT(12)
+#define MP2975_PRT_THRES_DIV_OV_EN	BIT(14)
+#define MP2975_DRMOS_KCS		GENMASK(13, 12)
+#define MP2975_PROT_DEV_OV_OFF		10
+#define MP2975_PROT_DEV_OV_ON		5
+#define MP2975_SENSE_AMPL		BIT(11)
+#define MP2975_SENSE_AMPL_UNIT		1
+#define MP2975_SENSE_AMPL_HALF		2
+#define MP2975_VIN_UV_LIMIT_UNIT	8
+
+#define MP2975_MAX_PHASE_RAIL1	8
+#define MP2975_MAX_PHASE_RAIL2	4
+#define MP2975_PAGE_NUM		2
+
+#define MP2975_RAIL2_FUNC	(PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT | \
+				 PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT | \
+				 PMBUS_PHASE_VIRTUAL)
+
+struct mp2975_data {
+	struct pmbus_driver_info info;
+	int vout_scale;
+	int vid_step[MP2975_PAGE_NUM];
+	int vref[MP2975_PAGE_NUM];
+	int vref_off[MP2975_PAGE_NUM];
+	int vout_max[MP2975_PAGE_NUM];
+	int vout_ov_fixed[MP2975_PAGE_NUM];
+	int vout_format[MP2975_PAGE_NUM];
+	int curr_sense_gain[MP2975_PAGE_NUM];
+};
+
+#define to_mp2975_data(x)  container_of(x, struct mp2975_data, info)
+
+static int mp2975_read_byte_data(struct i2c_client *client, int page, int reg)
+{
+	switch (reg) {
+	case PMBUS_VOUT_MODE:
+		/*
+		 * Enforce VOUT direct format, since device allows to set the
+		 * different formats for the different rails. Conversion from
+		 * VID to direct provided by driver internally, in case it is
+		 * necessary.
+		 */
+		return PB_VOUT_MODE_DIRECT;
+	default:
+		return -ENODATA;
+	}
+}
+
+static int
+mp2975_read_word_helper(struct i2c_client *client, int page, int phase, u8 reg,
+			u16 mask)
+{
+	int ret = pmbus_read_word_data(client, page, phase, reg);
+
+	return (ret > 0) ? ret & mask : ret;
+}
+
+static int
+mp2975_vid2direct(int vrf, int val)
+{
+	switch (vrf) {
+	case vr12:
+		if (val >= 0x01)
+			return 250 + (val - 1) * 5;
+		break;
+	case vr13:
+		if (val >= 0x01)
+			return 500 + (val - 1) * 10;
+		break;
+	case imvp9:
+		if (val >= 0x01)
+			return 200 + (val - 1) * 10;
+		break;
+	default:
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int
+mp2975_read_phase(struct i2c_client *client, struct mp2975_data *data,
+		  int page, int phase, u8 reg)
+{
+	int ph_curr, ret;
+
+	ret = pmbus_read_word_data(client, page, phase, reg);
+	if (ret < 0)
+		return ret;
+
+	if (!((phase + 1) % MP2975_PAGE_NUM))
+		ret >>= 8;
+	ret &= 0xff;
+
+	/*
+	 * Output value is calculated as: (READ_CSx / 80 – 1.23) / (Kcs * Rcs)
+	 * where:
+	 * - Kcs is the DrMOS current sense gain of power stage, which is
+	 *   obtained from the register MP2975_MFR_VR_CONFIG1, bits 13-12 with
+	 *   the following selection of DrMOS (data->curr_sense_gain[page]):
+	 *   00b - 5µA/A, 01b - 8.5µA/A, 10b - 9.7µA/A, 11b - 10µA/A.
+	 * - Rcs is the internal phase current sense resistor which is constant
+	 *   value 1kΩ.
+	 */
+	ph_curr = ret * 100 - 9800;
+
+	/*
+	 * Current phase sensing, providing by the device is not accurate
+	 * for the light load. This because sampling of current occurrence of
+	 * bit weight has a big deviation for light load. For handling such
+	 * case phase current is represented as the maximum between the value
+	 * calculated  above and total rail current divided by number phases.
+	 */
+	ret = pmbus_read_word_data(client, page, phase, PMBUS_READ_IOUT);
+	if (ret < 0)
+		return ret;
+
+	return max_t(int, DIV_ROUND_CLOSEST(ret, data->info.phases[page]),
+		     DIV_ROUND_CLOSEST(ph_curr, data->curr_sense_gain[page]));
+}
+
+static int
+mp2975_read_phases(struct i2c_client *client, struct mp2975_data *data,
+		   int page, int phase)
+{
+	int ret;
+
+	if (page) {
+		switch (phase) {
+		case 0 ... 1:
+			ret = mp2975_read_phase(client, data, page, phase,
+						MP2975_MFR_READ_CS7_8);
+			break;
+		case 2 ... 3:
+			ret = mp2975_read_phase(client, data, page, phase,
+						MP2975_MFR_READ_CS9_10);
+			break;
+		case 4 ... 5:
+			ret = mp2975_read_phase(client, data, page, phase,
+						MP2975_MFR_READ_CS11_12);
+			break;
+		default:
+			return -ENODATA;
+		}
+	} else {
+		switch (phase) {
+		case 0 ... 1:
+			ret = mp2975_read_phase(client, data, page, phase,
+						MP2975_MFR_READ_CS1_2);
+			break;
+		case 2 ... 3:
+			ret = mp2975_read_phase(client, data, page, phase,
+						MP2975_MFR_READ_CS3_4);
+			break;
+		case 4 ... 5:
+			ret = mp2975_read_phase(client, data, page, phase,
+						MP2975_MFR_READ_CS5_6);
+			break;
+		case 6 ... 7:
+			ret = mp2975_read_phase(client, data, page, phase,
+						MP2975_MFR_READ_CS7_8);
+			break;
+		case 8 ... 9:
+			ret = mp2975_read_phase(client, data, page, phase,
+						MP2975_MFR_READ_CS9_10);
+			break;
+		case 10 ... 11:
+			ret = mp2975_read_phase(client, data, page, phase,
+						MP2975_MFR_READ_CS11_12);
+			break;
+		default:
+			return -ENODATA;
+		}
+	}
+	return ret;
+}
+
+static int mp2975_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 mp2975_data *data = to_mp2975_data(info);
+	int ret;
+
+	switch (reg) {
+	case PMBUS_OT_FAULT_LIMIT:
+		ret = mp2975_read_word_helper(client, page, phase, reg,
+					      GENMASK(7, 0));
+		break;
+	case PMBUS_VIN_OV_FAULT_LIMIT:
+		ret = mp2975_read_word_helper(client, page, phase, reg,
+					      GENMASK(7, 0));
+		if (ret < 0)
+			return ret;
+
+		ret = DIV_ROUND_CLOSEST(ret, MP2975_VIN_UV_LIMIT_UNIT);
+		break;
+	case PMBUS_VOUT_OV_FAULT_LIMIT:
+		/*
+		 * Register provides two values for over-voltage protection
+		 * threshold for fixed (ovp2) and tracking (ovp1) modes. The
+		 * minimum of these two values is provided as over-voltage
+		 * fault alarm.
+		 */
+		ret = mp2975_read_word_helper(client, page, phase,
+					      MP2975_MFR_OVP_TH_SET,
+					      GENMASK(2, 0));
+		if (ret < 0)
+			return ret;
+
+		ret = min_t(int, data->vout_max[page] + 50 * (ret + 1),
+			    data->vout_ov_fixed[page]);
+		break;
+	case PMBUS_VOUT_UV_FAULT_LIMIT:
+		ret = mp2975_read_word_helper(client, page, phase,
+					      MP2975_MFR_UVP_SET,
+					      GENMASK(2, 0));
+		if (ret < 0)
+			return ret;
+
+		ret = DIV_ROUND_CLOSEST(data->vref[page] * 10 - 50 *
+					(ret + 1) * data->vout_scale, 10);
+		break;
+	case PMBUS_READ_VOUT:
+		ret = mp2975_read_word_helper(client, page, phase, reg,
+					      GENMASK(11, 0));
+		if (ret < 0)
+			return ret;
+
+		/*
+		 * READ_VOUT can be provided in VID or direct format. The
+		 * format type is specified by bit 15 of the register
+		 * MP2975_MFR_DC_LOOP_CTRL. The driver enforces VOUT direct
+		 * format, since device allows to set the different formats for
+		 * the different rails and also all VOUT limits registers are
+		 * provided in a direct format. In case format is VID - convert
+		 * to direct.
+		 */
+		if (data->vout_format[page] == vid)
+			ret = mp2975_vid2direct(info->vrm_version[page], ret);
+		break;
+	case PMBUS_VIRT_READ_POUT_MAX:
+		ret = mp2975_read_word_helper(client, page, phase,
+					      MP2975_MFR_READ_POUT_PK,
+					      GENMASK(12, 0));
+		if (ret < 0)
+			return ret;
+
+		ret = DIV_ROUND_CLOSEST(ret, 4);
+		break;
+	case PMBUS_VIRT_READ_IOUT_MAX:
+		ret = mp2975_read_word_helper(client, page, phase,
+					      MP2975_MFR_READ_IOUT_PK,
+					      GENMASK(12, 0));
+		if (ret < 0)
+			return ret;
+
+		ret = DIV_ROUND_CLOSEST(ret, 4);
+		break;
+	case PMBUS_READ_IOUT:
+		ret = mp2975_read_phases(client, data, page, phase);
+		if (ret < 0)
+			return ret;
+
+		break;
+	case PMBUS_UT_WARN_LIMIT:
+	case PMBUS_UT_FAULT_LIMIT:
+	case PMBUS_VIN_UV_WARN_LIMIT:
+	case PMBUS_VIN_UV_FAULT_LIMIT:
+	case PMBUS_VOUT_UV_WARN_LIMIT:
+	case PMBUS_VOUT_OV_WARN_LIMIT:
+	case PMBUS_VIN_OV_WARN_LIMIT:
+	case PMBUS_IIN_OC_FAULT_LIMIT:
+	case PMBUS_IOUT_OC_LV_FAULT_LIMIT:
+	case PMBUS_IIN_OC_WARN_LIMIT:
+	case PMBUS_IOUT_OC_WARN_LIMIT:
+	case PMBUS_IOUT_OC_FAULT_LIMIT:
+	case PMBUS_IOUT_UC_FAULT_LIMIT:
+	case PMBUS_POUT_OP_FAULT_LIMIT:
+	case PMBUS_POUT_OP_WARN_LIMIT:
+	case PMBUS_PIN_OP_WARN_LIMIT:
+		return -ENXIO;
+	default:
+		return -ENODATA;
+	}
+
+	return ret;
+}
+
+static int mp2975_identify_multiphase_rail2(struct i2c_client *client)
+{
+	int ret;
+
+	/*
+	 * Identify multiphase for rail 2 - could be from 0 to 4.
+	 * In case phase number is zero – only page zero is supported
+	 */
+	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 2);
+	if (ret < 0)
+		return ret;
+
+	/* Identify multiphase for rail 2 - could be from 0 to 4. */
+	ret = i2c_smbus_read_word_data(client, MP2975_MFR_VR_MULTI_CONFIG_R2);
+	if (ret < 0)
+		return ret;
+
+	ret &= GENMASK(2, 0);
+	return (ret >= 4) ? 4 : ret;
+}
+
+static void mp2975_set_phase_rail1(struct pmbus_driver_info *info)
+{
+	int i;
+
+	for (i = 0 ; i < info->phases[0]; i++)
+		info->pfunc[i] = PMBUS_HAVE_IOUT;
+}
+
+static void
+mp2975_set_phase_rail2(struct pmbus_driver_info *info, int num_phases)
+{
+	int i;
+
+	/* Set phases for rail 2 from upper to lower. */
+	for (i = 1; i <= num_phases; i++)
+		info->pfunc[MP2975_MAX_PHASE_RAIL1 - i] = PMBUS_HAVE_IOUT;
+}
+
+static int
+mp2975_identify_multiphase(struct i2c_client *client, struct mp2975_data *data,
+			   struct pmbus_driver_info *info)
+{
+	int num_phases2, ret;
+
+	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 2);
+	if (ret < 0)
+		return ret;
+
+	/* Identify multiphase for rail 1 - could be from 1 to 8. */
+	ret = i2c_smbus_read_word_data(client, MP2975_MFR_VR_MULTI_CONFIG_R1);
+	if (ret <= 0)
+		return ret;
+
+	info->phases[0] = ret & GENMASK(3, 0);
+
+	/*
+	 * The device provides a total of 8 PWM pins, and can be configured
+	 * to different phase count applications for rail 1 and rail 2.
+	 * Rail 1 can be set to 8 phases, while rail 2 can only be set to 4
+	 * phases at most. When rail 1’s phase count is configured as 0, rail
+	 * 1 operates with 1-phase DCM. When rail 2 phase count is configured
+	 * as 0, rail 2 is disabled.
+	 */
+	if (info->phases[0] > MP2975_MAX_PHASE_RAIL1)
+		return -EINVAL;
+
+	mp2975_set_phase_rail1(info);
+	num_phases2 = min(MP2975_MAX_PHASE_RAIL1 - info->phases[0],
+			  MP2975_MAX_PHASE_RAIL2);
+	if (info->phases[1] && info->phases[1] <= num_phases2)
+		mp2975_set_phase_rail2(info, num_phases2);
+
+	return 0;
+}
+
+static int
+mp2975_identify_vid(struct i2c_client *client, struct mp2975_data *data,
+		    struct pmbus_driver_info *info, u32 reg, int page,
+		    u32 imvp_bit, u32 vr_bit)
+{
+	int ret;
+
+	/* Identify VID mode and step selection. */
+	ret = i2c_smbus_read_word_data(client, reg);
+	if (ret < 0)
+		return ret;
+
+	if (ret & imvp_bit) {
+		info->vrm_version[page] = imvp9;
+		data->vid_step[page] = MP2975_PROT_DEV_OV_OFF;
+	} else if (ret & vr_bit) {
+		info->vrm_version[page] = vr12;
+		data->vid_step[page] = MP2975_PROT_DEV_OV_ON;
+	} else {
+		info->vrm_version[page] = vr13;
+		data->vid_step[page] = MP2975_PROT_DEV_OV_OFF;
+	}
+
+	return 0;
+}
+
+static int
+mp2975_identify_rails_vid(struct i2c_client *client, struct mp2975_data *data,
+			  struct pmbus_driver_info *info)
+{
+	int ret;
+
+	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 2);
+	if (ret < 0)
+		return ret;
+
+	/* Identify VID mode for rail 1. */
+	ret = mp2975_identify_vid(client, data, info,
+				  MP2975_MFR_VR_MULTI_CONFIG_R1, 0,
+				  MP2975_IMVP9_EN_R1, MP2975_VID_STEP_SEL_R1);
+	if (ret < 0)
+		return ret;
+
+	/* Identify VID mode for rail 2, if connected. */
+	if (info->phases[1])
+		ret = mp2975_identify_vid(client, data, info,
+					  MP2975_MFR_VR_MULTI_CONFIG_R2, 1,
+					  MP2975_IMVP9_EN_R2,
+					  MP2975_VID_STEP_SEL_R2);
+	return ret;
+}
+
+static int
+mp2975_current_sense_gain_get(struct i2c_client *client,
+			      struct mp2975_data *data)
+{
+	int i, ret;
+
+	/*
+	 * Obtain DrMOS current sense gain of power stage from the register
+	 * MP2975_MFR_VR_CONFIG1, bits 13-12. The value is selected as below:
+	 * 00b - 5µA/A, 01b - 8.5µA/A, 10b - 9.7µA/A, 11b - 10µA/A. Other
+	 * values are invalid.
+	 */
+	for (i = 0 ; i < data->info.pages; i++) {
+		ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, i);
+		if (ret < 0)
+			return ret;
+		ret = i2c_smbus_read_word_data(client,
+					       MP2975_MFR_VR_CONFIG1);
+		if (ret < 0)
+			return ret;
+
+		switch ((ret & MP2975_DRMOS_KCS) >> 12) {
+		case 0:
+			data->curr_sense_gain[i] = 50;
+			break;
+		case 1:
+			data->curr_sense_gain[i] = 85;
+			break;
+		case 2:
+			data->curr_sense_gain[i] = 97;
+			break;
+		default:
+			data->curr_sense_gain[i] = 100;
+			break;
+		}
+	}
+
+	return 0;
+}
+
+static int
+mp2975_vref_get(struct i2c_client *client, struct mp2975_data *data,
+		struct pmbus_driver_info *info)
+{
+	int ret;
+
+	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 3);
+	if (ret < 0)
+		return ret;
+
+	/* Get voltage reference value for rail 1. */
+	ret = i2c_smbus_read_word_data(client, MP2975_MFR_READ_VREF_R1);
+	if (ret < 0)
+		return ret;
+
+	data->vref[0] = ret * data->vid_step[0];
+
+	/* Get voltage reference value for rail 2, if connected. */
+	if (data->info.pages == MP2975_PAGE_NUM) {
+		ret = i2c_smbus_read_word_data(client, MP2975_MFR_READ_VREF_R2);
+		if (ret < 0)
+			return ret;
+
+		data->vref[1] = ret * data->vid_step[1];
+	}
+	return 0;
+}
+
+static int
+mp2975_vref_offset_get(struct i2c_client *client, struct mp2975_data *data,
+		       int page)
+{
+	int ret;
+
+	ret = i2c_smbus_read_word_data(client, MP2975_MFR_OVP_TH_SET);
+	if (ret < 0)
+		return ret;
+
+	switch ((ret & GENMASK(5, 3)) >> 3) {
+	case 1:
+		data->vref_off[page] = 140;
+		break;
+	case 2:
+		data->vref_off[page] = 220;
+		break;
+	case 4:
+		data->vref_off[page] = 400;
+		break;
+	default:
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int
+mp2975_vout_max_get(struct i2c_client *client, struct mp2975_data *data,
+		    struct pmbus_driver_info *info, int page)
+{
+	int ret;
+
+	/* Get maximum reference voltage of VID-DAC in VID format. */
+	ret = i2c_smbus_read_word_data(client, PMBUS_VOUT_MAX);
+	if (ret < 0)
+		return ret;
+
+	data->vout_max[page] = mp2975_vid2direct(info->vrm_version[page], ret &
+						 GENMASK(8, 0));
+	return 0;
+}
+
+static int
+mp2975_identify_vout_format(struct i2c_client *client,
+			    struct mp2975_data *data, int page)
+{
+	int ret;
+
+	ret = i2c_smbus_read_word_data(client, MP2975_MFR_DC_LOOP_CTRL);
+	if (ret < 0)
+		return ret;
+
+	if (ret & MP2975_VOUT_FORMAT)
+		data->vout_format[page] = vid;
+	else
+		data->vout_format[page] = direct;
+	return 0;
+}
+
+static int
+mp2975_vout_ov_scale_get(struct i2c_client *client, struct mp2975_data *data,
+			 struct pmbus_driver_info *info)
+{
+	int thres_dev, sense_ampl, ret;
+
+	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 0);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * Get divider for over- and under-voltage protection thresholds
+	 * configuration from the Advanced Options of Auto Phase Shedding and
+	 * decay register.
+	 */
+	ret = i2c_smbus_read_word_data(client, MP2975_MFR_APS_DECAY_ADV);
+	if (ret < 0)
+		return ret;
+	thres_dev = ret & MP2975_PRT_THRES_DIV_OV_EN ? MP2975_PROT_DEV_OV_ON :
+	                                               MP2975_PROT_DEV_OV_OFF;
+
+	/* Select the gain of remote sense amplifier. */
+	ret = i2c_smbus_read_word_data(client, PMBUS_VOUT_SCALE_LOOP);
+	if (ret < 0)
+		return ret;
+	sense_ampl = ret & MP2975_SENSE_AMPL ? MP2975_SENSE_AMPL_HALF :
+					       MP2975_SENSE_AMPL_UNIT;
+
+	data->vout_scale = sense_ampl * thres_dev;
+
+	return 0;
+}
+
+static int
+mp2975_vout_per_rail_config_get(struct i2c_client *client,
+				struct mp2975_data *data,
+				struct pmbus_driver_info *info)
+{
+	int i, ret;
+
+	for (i = 0; i < data->info.pages; i++) {
+		ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, i);
+		if (ret < 0)
+			return ret;
+
+		/* Obtain voltage reference offsets. */
+		ret = mp2975_vref_offset_get(client, data, i);
+		if (ret < 0)
+			return ret;
+
+		/* Obtain maximum voltage values. */
+		ret = mp2975_vout_max_get(client, data, info, i);
+		if (ret < 0)
+			return ret;
+
+		/*
+		 * Get VOUT format for READ_VOUT command : VID or direct.
+		 * Pages on same device can be configured with different
+		 * formats.
+		 */
+		ret = mp2975_identify_vout_format(client, data, i);
+		if (ret < 0)
+			return ret;
+
+		/*
+		 * Set over-voltage fixed value. Thresholds are provided as
+		 * fixed value, and tracking value. The minimum of them are
+		 * exposed as over-voltage critical threshold.
+		 */
+		data->vout_ov_fixed[i] = data->vref[i] +
+					 DIV_ROUND_CLOSEST(data->vref_off[i] *
+							   data->vout_scale,
+							   10);
+	}
+
+	return 0;
+}
+
+static struct pmbus_driver_info mp2975_info = {
+	.pages = 1,
+	.format[PSC_VOLTAGE_IN] = linear,
+	.format[PSC_VOLTAGE_OUT] = direct,
+	.format[PSC_TEMPERATURE] = direct,
+	.format[PSC_CURRENT_IN] = linear,
+	.format[PSC_CURRENT_OUT] = direct,
+	.format[PSC_POWER] = direct,
+	.m[PSC_TEMPERATURE] = 1,
+	.m[PSC_VOLTAGE_OUT] = 1,
+	.R[PSC_VOLTAGE_OUT] = 3,
+	.m[PSC_CURRENT_OUT] = 1,
+	.m[PSC_POWER] = 1,
+	.func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT |
+		PMBUS_HAVE_IIN | PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT |
+		PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_TEMP | PMBUS_HAVE_POUT |
+		PMBUS_HAVE_PIN | PMBUS_HAVE_STATUS_INPUT | PMBUS_PHASE_VIRTUAL,
+	.read_byte_data = mp2975_read_byte_data,
+	.read_word_data = mp2975_read_word_data,
+};
+
+static int mp2975_probe(struct i2c_client *client)
+{
+	struct pmbus_driver_info *info;
+	struct mp2975_data *data;
+	int ret;
+
+	data = devm_kzalloc(&client->dev, sizeof(struct mp2975_data),
+			    GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	memcpy(&data->info, &mp2975_info, sizeof(*info));
+	info = &data->info;
+
+	/* Identify multiphase configuration for rail 2. */
+	ret = mp2975_identify_multiphase_rail2(client);
+	if (ret < 0)
+		return ret;
+
+	if (ret) {
+		/* Two rails are connected. */
+		data->info.pages = MP2975_PAGE_NUM;
+		data->info.phases[1] = ret;
+		data->info.func[1] = MP2975_RAIL2_FUNC;
+	}
+
+	/* Identify multiphase configuration. */
+	ret = mp2975_identify_multiphase(client, data, info);
+	if (ret)
+		return ret;
+
+	/* Identify VID setting per rail. */
+	ret = mp2975_identify_rails_vid(client, data, info);
+	if (ret < 0)
+		return ret;
+
+	/* Obtain current sense gain of power stage. */
+	ret = mp2975_current_sense_gain_get(client, data);
+	if (ret)
+		return ret;
+
+	/* Obtain voltage reference values. */
+	ret = mp2975_vref_get(client, data, info);
+	if (ret)
+		return ret;
+
+	/* Obtain vout over-voltage scales. */
+	ret = mp2975_vout_ov_scale_get(client, data, info);
+	if (ret < 0)
+		return ret;
+
+	/* Obtain offsets, maximum and format for vout. */
+	ret = mp2975_vout_per_rail_config_get(client, data, info);
+	if (ret)
+		return ret;
+
+	return pmbus_do_probe(client, info);
+}
+
+static const struct i2c_device_id mp2975_id[] = {
+	{"mp2975", 0},
+	{}
+};
+
+MODULE_DEVICE_TABLE(i2c, mp2975_id);
+
+static const struct of_device_id __maybe_unused mp2975_of_match[] = {
+	{.compatible = "mps,mp2975"},
+	{}
+};
+MODULE_DEVICE_TABLE(of, mp2975_of_match);
+
+static struct i2c_driver mp2975_driver = {
+	.driver = {
+		.name = "mp2975",
+		.of_match_table = of_match_ptr(mp2975_of_match),
+	},
+	.probe_new = mp2975_probe,
+	.remove = pmbus_do_remove,
+	.id_table = mp2975_id,
+};
+
+module_i2c_driver(mp2975_driver);
+
+MODULE_AUTHOR("Vadim Pasternak <vadimp@nvidia.com>");
+MODULE_DESCRIPTION("PMBus driver for MPS MP2975 device");
+MODULE_LICENSE("GPL");