diff mbox series

[v2,2/2] hwmon: (pmbus) Add support for MPS Multi-phase mp2856/mp2857 controller

Message ID 20231211160519.21254-3-potin.lai.pt@gmail.com (mailing list archive)
State Accepted
Headers show
Series hwmon: (pmbus) Add support for MPS Multi-phase mp2856/mp2857 controller | expand

Commit Message

Potin Lai Dec. 11, 2023, 4:05 p.m. UTC
From: Peter Yin <peteryin.openbmc@gmail.com>

Add support for mp2856/mp2857 device from Monolithic Power Systems, Inc.
(MPS) vendor. This is a dual-loop, digital, multi-phase,
modulation controller.

Signed-off-by: Peter Yin <peteryin.openbmc@gmail.com>
Signed-off-by: Potin Lai <potin.lai.pt@gmail.com>
---
 Documentation/hwmon/index.rst  |   1 +
 Documentation/hwmon/mp2856.rst |  98 +++++++
 drivers/hwmon/pmbus/Kconfig    |   9 +
 drivers/hwmon/pmbus/Makefile   |   1 +
 drivers/hwmon/pmbus/mp2856.c   | 471 +++++++++++++++++++++++++++++++++
 5 files changed, 580 insertions(+)
 create mode 100644 Documentation/hwmon/mp2856.rst
 create mode 100644 drivers/hwmon/pmbus/mp2856.c

Comments

Guenter Roeck Dec. 17, 2023, 3:33 p.m. UTC | #1
On Tue, Dec 12, 2023 at 12:05:19AM +0800, Potin Lai wrote:
> From: Peter Yin <peteryin.openbmc@gmail.com>
> 
> Add support for mp2856/mp2857 device from Monolithic Power Systems, Inc.
> (MPS) vendor. This is a dual-loop, digital, multi-phase,
> modulation controller.
> 
> Signed-off-by: Peter Yin <peteryin.openbmc@gmail.com>
> Signed-off-by: Potin Lai <potin.lai.pt@gmail.com>

Applied, with reservations (because due to lack of datasheet it is all but
impossible to validate the code) and several fixups. So this driver comes
with even less warranty than usual.

CHECK: Alignment should match open parenthesis
#671: FILE: drivers/hwmon/pmbus/mp2856.c:413:
+	memcpy(data->max_phases, mp2856_max_phases[data->chip_id],
+		sizeof(data->max_phases));

CHECK: Please don't use multiple blank lines
#673: FILE: drivers/hwmon/pmbus/mp2856.c:415:
+
+

CHECK: Please don't use multiple blank lines
#707: FILE: drivers/hwmon/pmbus/mp2856.c:449:
+
+

Fix those, and use i2c_get_match_data().

_Please_ run your patches through checkpatch. The above is really
completely unnecessary and creates unnecessary extra work for others (me).

Guenter
Potin Lai Dec. 18, 2023, 2:43 a.m. UTC | #2
On Sun, Dec 17, 2023 at 11:33 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On Tue, Dec 12, 2023 at 12:05:19AM +0800, Potin Lai wrote:
> > From: Peter Yin <peteryin.openbmc@gmail.com>
> >
> > Add support for mp2856/mp2857 device from Monolithic Power Systems, Inc.
> > (MPS) vendor. This is a dual-loop, digital, multi-phase,
> > modulation controller.
> >
> > Signed-off-by: Peter Yin <peteryin.openbmc@gmail.com>
> > Signed-off-by: Potin Lai <potin.lai.pt@gmail.com>
>
> Applied, with reservations (because due to lack of datasheet it is all but
> impossible to validate the code) and several fixups. So this driver comes
> with even less warranty than usual.
>
> CHECK: Alignment should match open parenthesis
> #671: FILE: drivers/hwmon/pmbus/mp2856.c:413:
> +       memcpy(data->max_phases, mp2856_max_phases[data->chip_id],
> +               sizeof(data->max_phases));
>
> CHECK: Please don't use multiple blank lines
> #673: FILE: drivers/hwmon/pmbus/mp2856.c:415:
> +
> +
>
> CHECK: Please don't use multiple blank lines
> #707: FILE: drivers/hwmon/pmbus/mp2856.c:449:
> +
> +
>
> Fix those, and use i2c_get_match_data().
>
> _Please_ run your patches through checkpatch. The above is really
> completely unnecessary and creates unnecessary extra work for others (me).
>
> Guenter

Apologies for missing the style check issue, I will add "--strict"
when running checkpatch.pl in future.
And thank you for fixing the mistakes and applying the driver.

Potin
diff mbox series

Patch

diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index 641aa5d97add2..87dc65a6a0982 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -155,6 +155,7 @@  Hardware Monitoring Kernel Drivers
    mcp3021
    menf21bmc
    mlxreg-fan
+   mp2856
    mp2888
    mp2975
    mp5023
diff --git a/Documentation/hwmon/mp2856.rst b/Documentation/hwmon/mp2856.rst
new file mode 100644
index 0000000000000..af625c22b6ea7
--- /dev/null
+++ b/Documentation/hwmon/mp2856.rst
@@ -0,0 +1,98 @@ 
+.. SPDX-License-Identifier: GPL-2.0
+
+Kernel driver mp2856
+====================
+
+Supported chips:
+
+  * MPS MP2856
+
+    Prefix: 'mp2856'
+
+  * MPS MP2857
+
+    Prefix: 'mp2857'
+
+Author:
+
+	Peter Yin <peter.yin@quantatw.com>
+
+Description
+-----------
+
+This driver implements support for Monolithic Power Systems, Inc. (MPS)
+vendor dual-loop, digital, multi-phase controller MP2856/MP2857
+
+This device:
+
+- Supports up to two power rail.
+- Supports two pages 0 and 1 for and also pages 2 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: AMD SVI3 mode with 5-mV/LSB.
+
+Device supports:
+
+- SVID interface.
+- AVSBus interface.
+
+Device compliant 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: AMD SVI3.
+
+The driver provides the following sysfs attributes for current measurements:
+
+- indexes 1  for "iin";
+- indexes 2, 3 for "iout";
+
+**curr[1-3]_alarm**
+
+**curr[1-3]_input**
+
+**curr[1-3]_label**
+
+The driver provides the following sysfs attributes for voltage measurements.
+
+- indexes 1 for "vin";
+- indexes 2, 3 for "vout";
+
+**in[1-3]_crit**
+
+**in[1-3]_crit_alarm**
+
+**in[1-3]_input**
+
+**in[1-3]_label**
+
+**in[1-3]_lcrit**
+
+**in[1-3]_lcrit_alarm**
+
+The driver provides the following sysfs attributes for power measurements.
+
+- indexes 1 for "pin";
+- indexes 2, 3 for "pout";
+
+**power[1-3]_alarm**
+
+**power[1-3]_input**
+
+**power[1-3]_label**
+
+The driver provides the following sysfs attributes for temperature measurements.
+
+**temp[1-2]_crit**
+
+**temp[1-2]_crit_alarm**
+
+**temp[1-2]_input**
+
+**temp[1-2]_max**
+
+**temp[1-2]_max_alarm**
diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
index 17c98fca5bb6a..ad0e66e67bdef 100644
--- a/drivers/hwmon/pmbus/Kconfig
+++ b/drivers/hwmon/pmbus/Kconfig
@@ -299,6 +299,15 @@  config SENSORS_MAX8688
 	  This driver can also be built as a module. If so, the module will
 	  be called max8688.
 
+config SENSORS_MP2856
+	tristate "MPS MP2856"
+	help
+	  If you say yes here you get hardware monitoring support for MPS
+	  MP2856 MP2857 Dual Loop Digital Multi-Phase Controller.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called mp2856.
+
 config SENSORS_MP2888
 	tristate "MPS MP2888"
 	help
diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
index 212d9ca0acc97..f53b51b250ff8 100644
--- a/drivers/hwmon/pmbus/Makefile
+++ b/drivers/hwmon/pmbus/Makefile
@@ -32,6 +32,7 @@  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-$(CONFIG_SENSORS_MP2856)	+= mp2856.o
 obj-$(CONFIG_SENSORS_MP2888)	+= mp2888.o
 obj-$(CONFIG_SENSORS_MP2975)	+= mp2975.o
 obj-$(CONFIG_SENSORS_MP5023)	+= mp5023.o
diff --git a/drivers/hwmon/pmbus/mp2856.c b/drivers/hwmon/pmbus/mp2856.c
new file mode 100644
index 0000000000000..46b19af10f11b
--- /dev/null
+++ b/drivers/hwmon/pmbus/mp2856.c
@@ -0,0 +1,471 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Hardware monitoring driver for MPS2856/2857
+ * Monolithic Power Systems VR Controllers
+ *
+ * Copyright (C) 2023 Quanta Computer lnc.
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pmbus.h>
+#include "pmbus.h"
+
+/* Vendor specific registers. */
+#define MP2856_MFR_VR_MULTI_CONFIG_R1	0x0d
+#define MP2856_MFR_VR_MULTI_CONFIG_R2	0x1d
+
+#define MP2856_MUL1_BOOT_SR_R2		0x10
+#define MP2856_VR_ACTIVE		BIT(15)
+
+#define MP2856_MFR_VR_CONFIG2		0x5e
+#define MP2856_VOUT_MODE		BIT(11)
+
+#define MP2856_MFR_VR_CONFIG1		0x68
+#define MP2856_DRMOS_KCS		GENMASK(13, 12)
+
+#define MP2856_MFR_READ_CS1_2_R1	0x82
+#define MP2856_MFR_READ_CS3_4_R1	0x83
+#define MP2856_MFR_READ_CS5_6_R1	0x84
+#define MP2856_MFR_READ_CS7_8_R1	0x85
+#define MP2856_MFR_READ_CS9_10_R1	0x86
+#define MP2856_MFR_READ_CS11_12_R1	0x87
+
+#define MP2856_MFR_READ_CS1_2_R2	0x85
+#define MP2856_MFR_READ_CS3_4_R2	0x86
+#define MP2856_MFR_READ_CS5_6_R2	0x87
+
+#define MP2856_MAX_PHASE_RAIL1		8
+#define MP2856_MAX_PHASE_RAIL2		4
+
+#define MP2857_MAX_PHASE_RAIL1		12
+#define MP2857_MAX_PHASE_RAIL2		4
+
+#define MP2856_PAGE_NUM			2
+
+enum chips { mp2856, mp2857 };
+
+static const int mp2856_max_phases[][MP2856_PAGE_NUM] = {
+	[mp2856] = { MP2856_MAX_PHASE_RAIL1, MP2856_MAX_PHASE_RAIL2 },
+	[mp2857] = { MP2857_MAX_PHASE_RAIL1, MP2857_MAX_PHASE_RAIL2 },
+};
+
+static const struct i2c_device_id mp2856_id[] = {
+	{"mp2856", mp2856},
+	{"mp2857", mp2857},
+	{}
+};
+
+MODULE_DEVICE_TABLE(i2c, mp2856_id);
+
+struct mp2856_data {
+	struct pmbus_driver_info info;
+	int vout_format[MP2856_PAGE_NUM];
+	int curr_sense_gain[MP2856_PAGE_NUM];
+	int max_phases[MP2856_PAGE_NUM];
+	enum chips chip_id;
+};
+
+#define to_mp2856_data(x)	container_of(x, struct mp2856_data, info)
+
+#define MAX_LIN_MANTISSA	(1023 * 1000)
+#define MIN_LIN_MANTISSA	(511 * 1000)
+
+static u16 val2linear11(s64 val)
+{
+	s16 exponent = 0, mantissa;
+	bool negative = false;
+
+	if (val == 0)
+		return 0;
+
+	if (val < 0) {
+		negative = true;
+		val = -val;
+	}
+
+	/* Reduce large mantissa until it fits into 10 bit */
+	while (val >= MAX_LIN_MANTISSA && exponent < 15) {
+		exponent++;
+		val >>= 1;
+	}
+	/* Increase small mantissa to improve precision */
+	while (val < MIN_LIN_MANTISSA && exponent > -15) {
+		exponent--;
+		val <<= 1;
+	}
+
+	/* Convert mantissa from milli-units to units */
+	mantissa = clamp_val(DIV_ROUND_CLOSEST_ULL(val, 1000), 0, 0x3ff);
+
+	/* restore sign */
+	if (negative)
+		mantissa = -mantissa;
+
+	/* Convert to 5 bit exponent, 11 bit mantissa */
+	return (mantissa & 0x7ff) | ((exponent << 11) & 0xf800);
+}
+
+static int
+mp2856_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
+mp2856_read_vout(struct i2c_client *client, struct mp2856_data *data, int page,
+		 int phase, u8 reg)
+{
+	int ret;
+
+	ret = mp2856_read_word_helper(client, page, phase, reg,
+				      GENMASK(9, 0));
+	if (ret < 0)
+		return ret;
+
+	/* convert vout result to direct format */
+	ret = (data->vout_format[page] == vid) ?
+		((ret + 49) * 5) : ((ret * 1000) >> 8);
+
+	return ret;
+}
+
+static int
+mp2856_read_phase(struct i2c_client *client, struct mp2856_data *data,
+		  int page, int phase, u8 reg)
+{
+	int ret;
+	int val;
+
+	ret = pmbus_read_word_data(client, page, phase, reg);
+	if (ret < 0)
+		return ret;
+
+	if (!((phase + 1) % MP2856_PAGE_NUM))
+		ret >>= 8;
+	ret &= 0xff;
+
+	/*
+	 * Output value is calculated as: (READ_CSx * 12.5mV - 1.23V) / (Kcs * Rcs)
+	 */
+	val = (ret * 125) - 12300;
+
+	return val2linear11(val);
+}
+
+static int
+mp2856_read_phases(struct i2c_client *client, struct mp2856_data *data,
+		   int page, int phase)
+{
+	int ret;
+
+	if (page == 0) {
+		switch (phase) {
+		case 0 ... 1:
+			ret = mp2856_read_phase(client, data, page, phase,
+						MP2856_MFR_READ_CS1_2_R1);
+			break;
+		case 2 ... 3:
+			ret = mp2856_read_phase(client, data, page, phase,
+						MP2856_MFR_READ_CS3_4_R1);
+			break;
+		case 4 ... 5:
+			ret = mp2856_read_phase(client, data, page, phase,
+						MP2856_MFR_READ_CS5_6_R1);
+			break;
+		case 6 ... 7:
+			ret = mp2856_read_phase(client, data, page, phase,
+						MP2856_MFR_READ_CS7_8_R1);
+			break;
+		default:
+			return -ENODATA;
+		}
+	} else {
+		switch (phase) {
+		case 0 ... 1:
+			ret = mp2856_read_phase(client, data, page, phase,
+						MP2856_MFR_READ_CS1_2_R2);
+			break;
+		case 2 ... 3:
+			ret = mp2856_read_phase(client, data, page, phase,
+						MP2856_MFR_READ_CS1_2_R2);
+			break;
+		default:
+			return -ENODATA;
+		}
+	}
+	return ret;
+}
+
+static int
+mp2856_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 mp2856_data *data = to_mp2856_data(info);
+	int ret;
+
+	switch (reg) {
+	case PMBUS_READ_VOUT:
+		ret = mp2856_read_vout(client, data, page, phase, reg);
+		break;
+	case PMBUS_READ_IOUT:
+		if (phase != 0xff)
+			ret = mp2856_read_phases(client, data, page, phase);
+		else
+			ret = pmbus_read_word_data(client, page, phase, reg);
+		break;
+	default:
+		return -ENODATA;
+	}
+
+	return ret;
+}
+
+static int
+mp2856_read_byte_data(struct i2c_client *client, int page, int reg)
+{
+	switch (reg) {
+	case PMBUS_VOUT_MODE:
+		/* Enforce VOUT direct format. */
+		return PB_VOUT_MODE_DIRECT;
+	default:
+		return -ENODATA;
+	}
+}
+
+static int
+mp2856_identify_multiphase(struct i2c_client *client, u8 reg, u8 max_phase,
+			   u16 mask)
+{
+	int ret;
+
+	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 2);
+	if (ret < 0)
+		return ret;
+
+	ret = i2c_smbus_read_word_data(client, reg);
+	if (ret < 0)
+		return ret;
+
+	ret &= mask;
+	return (ret >= max_phase) ? max_phase : ret;
+}
+
+static int
+mp2856_identify_multiphase_rail1(struct i2c_client *client,
+				 struct mp2856_data *data)
+{
+	int ret, i;
+
+	ret = mp2856_identify_multiphase(client, MP2856_MFR_VR_MULTI_CONFIG_R1,
+					 MP2856_MAX_PHASE_RAIL1, GENMASK(3, 0));
+	if (ret < 0)
+		return ret;
+
+	data->info.phases[0] = (ret > data->max_phases[0]) ?
+				data->max_phases[0] : ret;
+
+	for (i = 0 ; i < data->info.phases[0]; i++)
+		data->info.pfunc[i] |= PMBUS_HAVE_IOUT;
+
+	return 0;
+}
+
+static int
+mp2856_identify_multiphase_rail2(struct i2c_client *client,
+				 struct mp2856_data *data)
+{
+	int ret, i;
+
+	ret = mp2856_identify_multiphase(client, MP2856_MFR_VR_MULTI_CONFIG_R2,
+					 MP2856_MAX_PHASE_RAIL2, GENMASK(2, 0));
+	if (ret < 0)
+		return ret;
+
+	data->info.phases[1] = (ret > data->max_phases[1]) ?
+				data->max_phases[1] : ret;
+
+	for (i = 0 ; i < data->info.phases[0]; i++)
+		data->info.pfunc[i] |= PMBUS_HAVE_IOUT;
+
+	return 0;
+}
+
+static int
+mp2856_current_sense_gain_get(struct i2c_client *client,
+			      struct mp2856_data *data)
+{
+	int i, ret;
+
+	/*
+	 * Obtain DrMOS current sense gain of power stage from the register
+	 * MP2856_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,
+					       MP2856_MFR_VR_CONFIG1);
+		if (ret < 0)
+			return ret;
+
+		switch ((ret & MP2856_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
+mp2856_identify_vout_format(struct i2c_client *client,
+			    struct mp2856_data *data)
+{
+	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;
+
+		ret = i2c_smbus_read_word_data(client, MP2856_MFR_VR_CONFIG2);
+		if (ret < 0)
+			return ret;
+
+		data->vout_format[i] = (ret & MP2856_VOUT_MODE) ? linear : vid;
+	}
+	return 0;
+}
+
+static bool
+mp2856_is_rail2_active(struct i2c_client *client)
+{
+	int ret;
+
+	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, 2);
+	if (ret < 0)
+		return true;
+
+	ret = i2c_smbus_read_word_data(client, MP2856_MUL1_BOOT_SR_R2);
+	if (ret < 0)
+		return true;
+
+	return (ret & MP2856_VR_ACTIVE) ? true : false;
+}
+
+static struct pmbus_driver_info mp2856_info = {
+	.pages = MP2856_PAGE_NUM,
+	.format[PSC_VOLTAGE_IN] = linear,
+	.format[PSC_VOLTAGE_OUT] = direct,
+	.format[PSC_TEMPERATURE] = linear,
+	.format[PSC_CURRENT_IN] = linear,
+	.format[PSC_CURRENT_OUT] = linear,
+	.format[PSC_POWER] = linear,
+	.m[PSC_VOLTAGE_OUT] = 1,
+	.R[PSC_VOLTAGE_OUT] = 3,
+	.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,
+	.func[1] = PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT | PMBUS_HAVE_IOUT |
+		PMBUS_HAVE_STATUS_IOUT | PMBUS_HAVE_POUT | PMBUS_HAVE_TEMP,
+	.read_byte_data = mp2856_read_byte_data,
+	.read_word_data = mp2856_read_word_data,
+};
+
+static int mp2856_probe(struct i2c_client *client)
+{
+	struct pmbus_driver_info *info;
+	struct mp2856_data *data;
+	int ret;
+
+	data = devm_kzalloc(&client->dev, sizeof(struct mp2856_data),
+			    GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	if (client->dev.of_node)
+		data->chip_id = (uintptr_t)of_device_get_match_data(&client->dev);
+	else
+		data->chip_id = i2c_match_id(mp2856_id, client)->driver_data;
+
+	memcpy(data->max_phases, mp2856_max_phases[data->chip_id],
+		sizeof(data->max_phases));
+
+
+	memcpy(&data->info, &mp2856_info, sizeof(*info));
+	info = &data->info;
+
+	/* Identify multiphase configuration. */
+	ret = mp2856_identify_multiphase_rail1(client, data);
+	if (ret < 0)
+		return ret;
+
+	if (mp2856_is_rail2_active(client)) {
+		ret = mp2856_identify_multiphase_rail2(client, data);
+		if (ret < 0)
+			return ret;
+	} else {
+		/* rail2 is not active */
+		info->pages = 1;
+	}
+
+	/* Obtain current sense gain of power stage. */
+	ret = mp2856_current_sense_gain_get(client, data);
+	if (ret)
+		return ret;
+
+	/* Identify vout format. */
+	ret = mp2856_identify_vout_format(client, data);
+	if (ret)
+		return ret;
+
+	/* set the device to page 0 */
+	i2c_smbus_write_byte_data(client, PMBUS_PAGE, 0);
+
+	return pmbus_do_probe(client, info);
+}
+
+
+static const struct of_device_id __maybe_unused mp2856_of_match[] = {
+	{.compatible = "mps,mp2856", .data = (void *)mp2856},
+	{.compatible = "mps,mp2857", .data = (void *)mp2857},
+	{}
+};
+MODULE_DEVICE_TABLE(of, mp2856_of_match);
+
+static struct i2c_driver mp2856_driver = {
+	.driver = {
+		.name = "mp2856",
+		.of_match_table = mp2856_of_match,
+	},
+	.probe = mp2856_probe,
+	.id_table = mp2856_id,
+};
+
+module_i2c_driver(mp2856_driver);
+
+MODULE_AUTHOR("Peter Yin <peter.yin@quantatw.com>");
+MODULE_DESCRIPTION("PMBus driver for MPS MP2856/MP2857 device");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS(PMBUS);