[PATCH hwmon-next v3 0/2] hwmon: (pmbus) Add support for MPS mp2975 controller

[PATCH hwmon-next v3 0/2] hwmon: (pmbus) Add support for MPS mp2975 controller

[Vadim Pasternak]

The patchset includes:
Patch #1 - introduction of the driver for mp2975 device,
	   documentation for mp2975 device driver.
Patch #2 - extending of binding documentation for trivial devices.

Vadim Pasternak (2):
  hwmon: (pmbus) Add support for MPS Multi-phase mp2975 controller
  dt-bindings: Add MP2975 voltage regulator device

 .../devicetree/bindings/trivial-devices.yaml       |   2 +
 Documentation/hwmon/mp2975.rst                     | 116 +++
 drivers/hwmon/pmbus/Kconfig                        |   9 +
 drivers/hwmon/pmbus/Makefile                       |   1 +
 drivers/hwmon/pmbus/mp2975.c                       | 812 +++++++++++++++++++++
 5 files changed, 940 insertions(+)
 create mode 100644 Documentation/hwmon/mp2975.rst
 create mode 100644 drivers/hwmon/pmbus/mp2975.c

-- 
2.11.0

[PATCH hwmon-next v3 1/2] hwmon: (pmbus) Add support for MPS Multi-phase mp2975 controller

[Vadim Pasternak]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset=y, Size: 27746 bytes --]

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>
---
v1->v2
 Comments pointed out by Guenter:
 - Add doc fail to the patch#1 (it was sent as separate patch).
 - Use standard define for VOUT mode format.
 - Simplify logic in mp2975_read_phase().
 - Simplify calculation of phase current in mp2975_read_phase().
 - Modify return code handling in mp2975_read_word_data().
 - Add missed error handling in mp2975_read_word_data().
 - Drop 'fallthrough;' in  mp2975_read_word_data().
 - Handle error code in mp2975_identify_multiphase_rail2().
 - Handle error code in mp2975_identify_multiphase().
 - Drop 'goto' in mp2975_vout_per_rail_config_get() and mp2975_probe().
---
 Documentation/hwmon/mp2975.rst | 116 ++++++
 drivers/hwmon/pmbus/Kconfig    |   9 +
 drivers/hwmon/pmbus/Makefile   |   1 +
 drivers/hwmon/pmbus/mp2975.c   | 812 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 938 insertions(+)
 create mode 100644 Documentation/hwmon/mp2975.rst
 create mode 100644 drivers/hwmon/pmbus/mp2975.c

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 e35db489b76f..1e6157e85437 100644
--- a/drivers/hwmon/pmbus/Kconfig
+++ b/drivers/hwmon/pmbus/Kconfig
@@ -200,6 +200,15 @@ 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 c4b15db996ad..0e2832e73cfc 100644
--- a/drivers/hwmon/pmbus/Makefile
+++ b/drivers/hwmon/pmbus/Makefile
@@ -23,6 +23,7 @@ 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..ba758ab744d1
--- /dev/null
+++ b/drivers/hwmon/pmbus/mp2975.c
@@ -0,0 +1,812 @@
+// 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;
+
+	return 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 max_rail, i;
+
+	/* Set phases for rail 2 from upper to lower. */
+	max_rail = info->phases[1] % (MP2975_MAX_PHASE_RAIL2 - 1);
+	for (i = 1; i <= max_rail; i++)
+		info->pfunc[MP2975_MAX_PHASE_RAIL1 - i] = PMBUS_HAVE_IOUT;
+}
+
+static int mp2975_set_multiphase_rail2(struct pmbus_driver_info *info)
+{
+	switch (info->phases[1]) {
+	case 1 ... 7:
+		mp2975_set_phase_rail2(info);
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int
+mp2975_identify_multiphase(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 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;
+	if (ret == 0)
+		return -EINVAL;
+
+	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.
+	 */
+	switch (info->phases[0]) {
+	case 1 ... 4:
+		mp2975_set_phase_rail1(info);
+		return mp2975_set_multiphase_rail2(info);
+	case 5:
+		mp2975_set_phase_rail1(info);
+		switch (info->phases[1]) {
+		case 1 ... 3:
+			return mp2975_set_multiphase_rail2(info);
+		default:
+			return 0;
+		}
+	case 6:
+		mp2975_set_phase_rail1(info);
+		switch (info->phases[1]) {
+		case 1 ... 2:
+			return mp2975_set_multiphase_rail2(info);
+		default:
+			return 0;
+		}
+	case 7:
+		mp2975_set_phase_rail1(info);
+		switch (info->phases[1]) {
+		case 1:
+			return mp2975_set_multiphase_rail2(info);
+		default:
+			return 0;
+		}
+	case 8:
+		mp2975_set_phase_rail1(info);
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+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;
+		case 3:
+			data->curr_sense_gain[i] = 100;
+			break;
+		default:
+			return -EINVAL;
+		}
+	}
+
+	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)
+		thres_dev = ret & MP2975_PRT_THRES_DIV_OV_EN ?
+			    MP2975_PROT_DEV_OV_ON : MP2975_PROT_DEV_OV_OFF;
+	else
+		return ret;
+
+	/* Select the gain of remote sense amplifier. */
+	ret = i2c_smbus_read_word_data(client, PMBUS_VOUT_SCALE_LOOP);
+	if (ret >= 0)
+		sense_ampl = ret & MP2975_SENSE_AMPL ? MP2975_SENSE_AMPL_HALF :
+			     MP2975_SENSE_AMPL_UNIT;
+	else
+		return ret;
+
+	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,
+			const struct i2c_device_id *id)
+{
+	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 railes 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, id, 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 = 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");
-- 
2.11.0

[PATCH hwmon-next v3 2/2] dt-bindings: Add MP2975 voltage regulator device

[Vadim Pasternak]

Monolithic Power Systems, Inc. (MPS) dual-loop, digital, multi-phase
controller.

Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>
---
v2->v3
 - Fix after 'make dt_binding_check'.
---
 Documentation/devicetree/bindings/trivial-devices.yaml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/trivial-devices.yaml b/Documentation/devicetree/bindings/trivial-devices.yaml
index 4ace8039840a..b2e994bc00af 100644
--- a/Documentation/devicetree/bindings/trivial-devices.yaml
+++ b/Documentation/devicetree/bindings/trivial-devices.yaml
@@ -80,6 +80,8 @@ properties:
           - fsl,mpl3115
             # MPR121: Proximity Capacitive Touch Sensor Controller
           - fsl,mpr121
+            # Monolithic Power Systems Inc. multi-phase controller mp2975
+          - mps,mp2975
             # G751: Digital Temperature Sensor and Thermal Watchdog with Two-Wire Interface
           - gmt,g751
             # Infineon IR38064 Voltage Regulator
-- 
2.11.0

Re: [PATCH hwmon-next v3 1/2] hwmon: (pmbus) Add support for MPS Multi-phase mp2975 controller

[Guenter Roeck]

On Thu, Sep 24, 2020 at 12:02:12AM +0300, Vadim Pasternak wrote:
> 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>
> ---
> v1->v2
>  Comments pointed out by Guenter:
>  - Add doc fail to the patch#1 (it was sent as separate patch).
>  - Use standard define for VOUT mode format.
>  - Simplify logic in mp2975_read_phase().
>  - Simplify calculation of phase current in mp2975_read_phase().
>  - Modify return code handling in mp2975_read_word_data().
>  - Add missed error handling in mp2975_read_word_data().
>  - Drop 'fallthrough;' in  mp2975_read_word_data().
>  - Handle error code in mp2975_identify_multiphase_rail2().
>  - Handle error code in mp2975_identify_multiphase().
>  - Drop 'goto' in mp2975_vout_per_rail_config_get() and mp2975_probe().
> ---
>  Documentation/hwmon/mp2975.rst | 116 ++++++
>  drivers/hwmon/pmbus/Kconfig    |   9 +
>  drivers/hwmon/pmbus/Makefile   |   1 +
>  drivers/hwmon/pmbus/mp2975.c   | 812 +++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 938 insertions(+)
>  create mode 100644 Documentation/hwmon/mp2975.rst
>  create mode 100644 drivers/hwmon/pmbus/mp2975.c
> 
> 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 e35db489b76f..1e6157e85437 100644
> --- a/drivers/hwmon/pmbus/Kconfig
> +++ b/drivers/hwmon/pmbus/Kconfig
> @@ -200,6 +200,15 @@ 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 c4b15db996ad..0e2832e73cfc 100644
> --- a/drivers/hwmon/pmbus/Makefile
> +++ b/drivers/hwmon/pmbus/Makefile
> @@ -23,6 +23,7 @@ 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..ba758ab744d1
> --- /dev/null
> +++ b/drivers/hwmon/pmbus/mp2975.c
> @@ -0,0 +1,812 @@
> +// 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;
> +
> +	return ret;

One return statement should be enough. Also, while it doesn't hurt,
the () is really unnecessary.

> +}
> +
> +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 max_rail, i;
> +
> +	/* Set phases for rail 2 from upper to lower. */
> +	max_rail = info->phases[1] % (MP2975_MAX_PHASE_RAIL2 - 1);

If info->phases[1] is 4, info->phases[1] % (MP2975_MAX_PHASE_RAIL2 - 1)
is 4 % 3 == 1.  So in that case only index 3 will be set. If the number of
phases is 3, nothing will be set (3 % 3 == 0). This is ... not easy to
understand.

> +	for (i = 1; i <= max_rail; i++)
> +		info->pfunc[MP2975_MAX_PHASE_RAIL1 - i] = PMBUS_HAVE_IOUT;

So ... i can be 1..3. This never sets a value for info->pfunc[0]. If the number
of phases is 1 or 4, it will (only) set info->pfunc[3]. And so on.

I think this function warrants a bit of explanation. I for sure can't follow it.

> +}
> +
> +static int mp2975_set_multiphase_rail2(struct pmbus_driver_info *info)
> +{
> +	switch (info->phases[1]) {
> +	case 1 ... 7:

... but rail 2 can only support up to 4 phases ?

> +		mp2975_set_phase_rail2(info);
> +		return 0;
> +	default:
> +		return -EINVAL;
> +	}

You are going quite overboard with error checking on the number of phases
for rail 2. mp2975_identify_multiphase_rail2() already limits the number
to 4. The calling code, in all but one places, already checks the range,
and there is no real reason to do the remaining check here.

> +}
> +
> +static int
> +mp2975_identify_multiphase(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 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;
> +	if (ret == 0)
> +		return -EINVAL;
> +
> +	info->phases[0] = ret & GENMASK(3, 0);

The above makes me wonder: Can info->phases[0] ever be 0 ? We checked for
ret == 0 above, but I wonder if it should be ret & GENMASK(3, 0) == 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.
> +	 */
> +	switch (info->phases[0]) {
> +	case 1 ... 4:
> +		mp2975_set_phase_rail1(info);
> +		return mp2975_set_multiphase_rail2(info);

Is info->phases[1] == 0 indeed a bug here, ie rail 2 _must_ be enabled
if rail 1 is configured for 1..4 phases ? That doesn't exactly match the
comment above.

> +	case 5:
> +		mp2975_set_phase_rail1(info);
> +		switch (info->phases[1]) {
> +		case 1 ... 3:
> +			return mp2975_set_multiphase_rail2(info);
> +		default:
> +			return 0;
> +		}
> +	case 6:
> +		mp2975_set_phase_rail1(info);
> +		switch (info->phases[1]) {
> +		case 1 ... 2:
> +			return mp2975_set_multiphase_rail2(info);
> +		default:
> +			return 0;
> +		}
> +	case 7:
> +		mp2975_set_phase_rail1(info);
> +		switch (info->phases[1]) {
> +		case 1:
> +			return mp2975_set_multiphase_rail2(info);
> +		default:
> +			return 0;
> +		}
> +	case 8:
> +		mp2975_set_phase_rail1(info);
> +		return 0;

So let's see ... mp2975_set_phase_rail1(info) is always called except if rail 1
has no phases. In that case we bail out. The number of valid phases for rail 2
is, for the most part, min(8 - info->phases[0], 4).

Hmm... something like

	if (info->phases[0] == 0 || info->phases[0] > MP2975_MAX_PHASE_RAIL1)
		return -EINVAL;
	if (info->phases[0] < 5 && !info->phases[1])		// really ?
		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);

should do pretty much the same and would be much easier to read.

> +	default:
> +		return -EINVAL;

This seems to answer my question. With that, the "if (ret == 0)" check above
is really superfluous since it is again checked here.

> +	}
> +}
> +
> +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)

Line length limit is now 100, so you should not need that many continuation
lines.

> +{
> +	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;
> +		case 3:
> +			data->curr_sense_gain[i] = 100;
> +			break;
> +		default:
> +			return -EINVAL;

Can't really get here. If the compiler complains it might be better to just add
the default: case to one of the other cases.

> +		}
> +	}
> +
> +	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)
> +		thres_dev = ret & MP2975_PRT_THRES_DIV_OV_EN ?
> +			    MP2975_PROT_DEV_OV_ON : MP2975_PROT_DEV_OV_OFF;
> +	else
> +		return ret;
> +
> +	/* Select the gain of remote sense amplifier. */
> +	ret = i2c_smbus_read_word_data(client, PMBUS_VOUT_SCALE_LOOP);
> +	if (ret >= 0)
> +		sense_ampl = ret & MP2975_SENSE_AMPL ? MP2975_SENSE_AMPL_HALF :
> +			     MP2975_SENSE_AMPL_UNIT;
> +	else
> +		return ret;
> +
> +	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,
> +			const struct i2c_device_id *id)
> +{
> +	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 railes are connected. */

rails

> +		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, id, 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 = 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");