Message-ID: <c1dd9473-262c-433b-994b-4bc70afc93c8@roeck-us.net>
Date: Mon, 8 Sep 2025 06:36:21 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: wenswang@...h.net, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, jdelvare@...e.com, corbet@....net
Cc: devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-hwmon@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH 2/2] hwmon: add MP2925 and MP2929 driver

On 9/8/25 04:01, wenswang@...h.net wrote:
> From: Wensheng Wang <wenswang@...h.net>
> 
> Add support for MPS VR mp2925 and mp2929 controller. This driver exposes
> telemetry and limit value readings and writtings.
> 
> Signed-off-by: Wensheng Wang <wenswang@...h.net>
> ---
>   Documentation/hwmon/index.rst  |   1 +
>   Documentation/hwmon/mp2925.rst | 151 ++++++++++++++++
>   MAINTAINERS                    |   7 +
>   drivers/hwmon/pmbus/Kconfig    |   9 +
>   drivers/hwmon/pmbus/Makefile   |   1 +
>   drivers/hwmon/pmbus/mp2925.c   | 312 +++++++++++++++++++++++++++++++++
>   6 files changed, 481 insertions(+)
>   create mode 100644 Documentation/hwmon/mp2925.rst
>   create mode 100644 drivers/hwmon/pmbus/mp2925.c
> 
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index d292a86ac5da..95bcf71ff6d9 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -175,6 +175,7 @@ Hardware Monitoring Kernel Drivers
>      mp2856
>      mp2888
>      mp2891
> +   mp2925
>      mp2975
>      mp2993
>      mp5023
> diff --git a/Documentation/hwmon/mp2925.rst b/Documentation/hwmon/mp2925.rst
> new file mode 100644
> index 000000000000..63eda215b6cb
> --- /dev/null
> +++ b/Documentation/hwmon/mp2925.rst
> @@ -0,0 +1,151 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +Kernel driver mp2925
> +====================
> +
> +Supported chips:
> +
> +  * MPS mp2925
> +
> +    Prefix: 'mp2925'
> +
> +  * MPS mp2929
> +
> +    Prefix: 'mp2929'
> +
> +Author:
> +
> +	Wensheng Wang <wenswang@...h.net>
> +
> +Description
> +-----------
> +
> +This driver implements support for Monolithic Power Systems, Inc. (MPS)
> +MP2925 Dual Loop Digital Multi-phase Controller.
> +
> +Device compliant with:
> +
> +- PMBus rev 1.3 interface.
> +
> +The driver exports the following attributes via the 'sysfs' files
> +for input voltage:
> +
> +**in1_input**
> +
> +**in1_label**
> +
> +**in1_crit**
> +
> +**in1_crit_alarm**
> +
> +**in1_lcrit**
> +
> +**in1_lcrit_alarm**
> +
> +**in1_max**
> +
> +**in1_max_alarm**
> +
> +**in1_min**
> +
> +**in1_min_alarm**
> +
> +The driver provides the following attributes for output voltage:
> +
> +**in2_input**
> +
> +**in2_label**
> +
> +**in2_crit**
> +
> +**in2_crit_alarm**
> +
> +**in2_lcrit**
> +
> +**in2_lcrit_alarm**
> +
> +**in3_input**
> +
> +**in3_label**
> +
> +**in3_crit**
> +
> +**in3_crit_alarm**
> +
> +**in3_lcrit**
> +
> +**in3_lcrit_alarm**
> +
> +The driver provides the following attributes for input current:
> +
> +**curr1_input**
> +
> +**curr1_label**
> +
> +The driver provides the following attributes for output current:
> +
> +**curr2_input**
> +
> +**curr2_label**
> +
> +**curr2_crit**
> +
> +**curr2_crit_alarm**
> +
> +**curr2_max**
> +
> +**curr2_max_alarm**
> +
> +**curr3_input**
> +
> +**curr3_label**
> +
> +**curr3_crit**
> +
> +**curr3_crit_alarm**
> +
> +**curr3_max**
> +
> +**curr3_max_alarm**
> +
> +The driver provides the following attributes for input power:
> +
> +**power1_input**
> +
> +**power1_label**
> +
> +**power2_input**
> +
> +**power2_label**
> +
> +The driver provides the following attributes for output power:
> +
> +**power3_input**
> +
> +**power3_label**
> +
> +**power4_input**
> +
> +**power4_label**
> +
> +The driver provides the following attributes for temperature:
> +
> +**temp1_input**
> +
> +**temp1_crit**
> +
> +**temp1_crit_alarm**
> +
> +**temp1_max**
> +
> +**temp1_max_alarm**
> +
> +**temp2_input**
> +
> +**temp2_crit**
> +
> +**temp2_crit_alarm**
> +
> +**temp2_max**
> +
> +**temp2_max_alarm**
> diff --git a/MAINTAINERS b/MAINTAINERS
> index cd7ff55b5d32..6444cf742098 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -17184,6 +17184,13 @@ S:	Maintained
>   F:	Documentation/hwmon/mp2891.rst
>   F:	drivers/hwmon/pmbus/mp2891.c
>   
> +MPS MP2925 DRIVER
> +M:	Noah Wang <wenswang@...h.net>
> +L:	linux-hwmon@...r.kernel.org
> +S:	Maintained
> +F:	Documentation/hwmon/mp2925.rst
> +F:	drivers/hwmon/pmbus/mp2925.c
> +
>   MPS MP2993 DRIVER
>   M:	Noah Wang <noahwang.wang@...look.com>
>   L:	linux-hwmon@...r.kernel.org
> diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
> index 55e492452ce8..d0e1eb500215 100644
> --- a/drivers/hwmon/pmbus/Kconfig
> +++ b/drivers/hwmon/pmbus/Kconfig
> @@ -391,6 +391,15 @@ config SENSORS_MP2891
>         This driver can also be built as a module. If so, the module will
>         be called mp2891.
>   
> +config SENSORS_MP2925
> +    tristate "MPS MP2925"
> +    help
> +      If you say yes here you get hardware monitoring support for MPS
> +      MP2925 Dual Loop Digital Multi-Phase Controller.
> +
> +      This driver can also be built as a module. If so, the module will
> +      be called mp2925.
> +
>   config SENSORS_MP2975
>   	tristate "MPS MP2975"
>   	help
> diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
> index 29cd8a3317d2..64c1b03bf47b 100644
> --- a/drivers/hwmon/pmbus/Makefile
> +++ b/drivers/hwmon/pmbus/Makefile
> @@ -39,6 +39,7 @@ obj-$(CONFIG_SENSORS_MAX8688)	+= max8688.o
>   obj-$(CONFIG_SENSORS_MP2856)	+= mp2856.o
>   obj-$(CONFIG_SENSORS_MP2888)	+= mp2888.o
>   obj-$(CONFIG_SENSORS_MP2891)	+= mp2891.o
> +obj-$(CONFIG_SENSORS_MP2925)	+= mp2925.o
>   obj-$(CONFIG_SENSORS_MP2975)	+= mp2975.o
>   obj-$(CONFIG_SENSORS_MP2993)	+= mp2993.o
>   obj-$(CONFIG_SENSORS_MP5023)	+= mp5023.o
> diff --git a/drivers/hwmon/pmbus/mp2925.c b/drivers/hwmon/pmbus/mp2925.c
> new file mode 100644
> index 000000000000..453995fca3bf
> --- /dev/null
> +++ b/drivers/hwmon/pmbus/mp2925.c
> @@ -0,0 +1,312 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Hardware monitoring driver for MPS Multi-phase Digital VR Controllers(MP2925)
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include "pmbus.h"
> +
> +/*
> + * Vender specific register MFR_VR_MULTI_CONFIG(0x08).
> + * This register is used to obtain vid scale.
> + */
> +#define MFR_VR_MULTI_CONFIG	0x08
> +
> +#define MP2925_VOUT_DIV	512
> +#define MP2925_VOUT_OVUV_UINT	195
> +#define MP2925_VOUT_OVUV_DIV	100
> +
> +#define MP2925_PAGE_NUM	2
> +
> +#define MP2925_RAIL1_FUNC	(PMBUS_HAVE_VIN | PMBUS_HAVE_PIN | \
> +							 PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT | \
> +							 PMBUS_HAVE_POUT | PMBUS_HAVE_TEMP | \
> +							 PMBUS_HAVE_STATUS_VOUT | \
> +							 PMBUS_HAVE_STATUS_IOUT | \
> +							 PMBUS_HAVE_STATUS_TEMP | \
> +							 PMBUS_HAVE_STATUS_INPUT)
> +
> +#define MP2925_RAIL2_FUNC	(PMBUS_HAVE_PIN | PMBUS_HAVE_VOUT | \
> +							 PMBUS_HAVE_IOUT | PMBUS_HAVE_POUT | \
> +							 PMBUS_HAVE_TEMP | PMBUS_HAVE_IIN | \
> +							 PMBUS_HAVE_STATUS_VOUT | \
> +							 PMBUS_HAVE_STATUS_IOUT | \
> +							 PMBUS_HAVE_STATUS_TEMP | \
> +							 PMBUS_HAVE_STATUS_INPUT)
> +
> +struct mp2925_data {
> +	struct pmbus_driver_info info;
> +	int vout_scale[MP2925_PAGE_NUM];
> +};
> +
> +#define to_mp2925_data(x) container_of(x, struct mp2925_data, info)
> +
> +static u16 mp2925_linear_exp_transfer(u16 word, u16 expect_exponent)
> +{
> +	s16 exponent, mantissa, target_exponent;
> +
> +	exponent = ((s16)word) >> 11;
> +	mantissa = ((s16)((word & 0x7ff) << 5)) >> 5;
> +	target_exponent = (s16)((expect_exponent & 0x1f) << 11) >> 11;
> +
> +	if (exponent > target_exponent)
> +		mantissa = mantissa << (exponent - target_exponent);
> +	else
> +		mantissa = mantissa >> (target_exponent - exponent);
> +
> +	return (mantissa & 0x7ff) | ((expect_exponent << 11) & 0xf800);
> +}
> +
> +static int mp2925_read_byte_data(struct i2c_client *client, int page, int reg)
> +{
> +	int ret;
> +
> +	switch (reg) {
> +	case PMBUS_VOUT_MODE:
> +		/*
> +		 * The MP2925 does not follow standard PMBus protocol completely,
> +		 * and the calculation of vout in this driver is based on direct
> +		 * format. As a result, the format of vout is enforced to direct.
> +		 */
> +		ret = PB_VOUT_MODE_DIRECT;
> +		break;
> +	default:
> +		ret = -ENODATA;
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
> +static int mp2925_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 mp2925_data *data = to_mp2925_data(info);
> +	int ret;
> +
> +	switch (reg) {
> +	case PMBUS_READ_VOUT:
> +		ret = pmbus_read_word_data(client, page, phase, reg);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = DIV_ROUND_CLOSEST((ret & GENMASK(11, 0)) * data->vout_scale[page],
> +					MP2925_VOUT_DIV);
> +		break;
> +	case PMBUS_VOUT_OV_FAULT_LIMIT:
> +	case PMBUS_VOUT_UV_FAULT_LIMIT:
> +		ret = pmbus_read_word_data(client, page, phase, reg);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = DIV_ROUND_CLOSEST((ret & GENMASK(11, 0)) * MP2925_VOUT_OVUV_UINT,
> +					MP2925_VOUT_OVUV_DIV);
> +		break;
> +	case PMBUS_STATUS_WORD:
> +	case PMBUS_READ_VIN:
> +	case PMBUS_READ_IOUT:
> +	case PMBUS_READ_POUT:
> +	case PMBUS_READ_PIN:
> +	case PMBUS_READ_IIN:
> +	case PMBUS_READ_TEMPERATURE_1:
> +	case PMBUS_VIN_OV_FAULT_LIMIT:
> +	case PMBUS_VIN_OV_WARN_LIMIT:
> +	case PMBUS_VIN_UV_WARN_LIMIT:
> +	case PMBUS_VIN_UV_FAULT_LIMIT:
> +	case PMBUS_IOUT_OC_FAULT_LIMIT:
> +	case PMBUS_IOUT_OC_WARN_LIMIT:
> +	case PMBUS_OT_FAULT_LIMIT:
> +	case PMBUS_OT_WARN_LIMIT:
> +		ret = -ENODATA;
> +		break;
> +	default:
> +		ret = -EINVAL;
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
> +static int mp2925_write_word_data(struct i2c_client *client, int page, int reg,
> +				  u16 word)
> +{
> +	int ret;
> +
> +	switch (reg) {
> +	case PMBUS_VIN_OV_FAULT_LIMIT:
> +	case PMBUS_VIN_OV_WARN_LIMIT:
> +	case PMBUS_VIN_UV_WARN_LIMIT:
> +	case PMBUS_VIN_UV_FAULT_LIMIT:
> +		/*
> +		 * The PMBUS_VIN_OV_FAULT_LIMIT, PMBUS_VIN_OV_WARN_LIMIT,
> +		 * PMBUS_VIN_UV_WARN_LIMIT and PMBUS_VIN_UV_FAULT_LIMIT
> +		 * of MP2925 is linear11 format, and the exponent is a
> +		 * constant value(5'b11100)， so the exponent of word
> +		 * parameter should be converted to 5'b11100(0x1C).
> +		 */
> +		ret = pmbus_write_word_data(client, page, reg,
> +					    mp2925_linear_exp_transfer(word, 0x1C));
> +		if (ret < 0)
> +			return ret;
> +		break;
> +	case PMBUS_VOUT_OV_FAULT_LIMIT:
> +	case PMBUS_VOUT_UV_FAULT_LIMIT:
> +		ret = pmbus_write_word_data(client, page, reg,
> +					    (ret & ~GENMASK(11, 0)) |
> +				FIELD_PREP(GENMASK(11, 0),
> +					   DIV_ROUND_CLOSEST(word * MP2925_VOUT_OVUV_DIV,
> +							     MP2925_VOUT_OVUV_UINT)));
> +		break;
> +	case PMBUS_OT_FAULT_LIMIT:
> +	case PMBUS_OT_WARN_LIMIT:
> +		/*
> +		 * The PMBUS_OT_FAULT_LIMIT and PMBUS_OT_WARN_LIMIT of
> +		 * MP2925 is linear11 format, and the exponent is a
> +		 * constant value(5'b00000), so the exponent of word
> +		 * parameter should be converted to 5'b00000.
> +		 */
> +		ret = pmbus_write_word_data(client, page, reg,
> +					    mp2925_linear_exp_transfer(word, 0x00));
> +		if (ret < 0)
> +			return ret;
> +		break;
> +	case PMBUS_IOUT_OC_FAULT_LIMIT:
> +	case PMBUS_IOUT_OC_WARN_LIMIT:
> +		/*
> +		 * The PMBUS_IOUT_OC_FAULT_LIMIT and PMBUS_IOUT_OC_WARN_LIMIT
> +		 * of MP2925 is linear11 format, and the exponent is a
> +		 * can not be changed.
> +		 */
> +		ret = pmbus_read_word_data(client, page, 0xff, reg);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = pmbus_write_word_data(client, page, reg,
> +					    mp2925_linear_exp_transfer(word,
> +								       FIELD_GET(GENMASK(15, 11),
> +										 ret)));
> +		break;
> +	default:
> +		ret = -EINVAL;
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
> +static int
> +mp2925_identify_vout_scale(struct i2c_client *client, struct pmbus_driver_info *info,
> +			   int page)
> +{
> +	struct mp2925_data *data = to_mp2925_data(info);
> +	int ret;
> +
> +	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, page);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = i2c_smbus_read_byte_data(client, PMBUS_VOUT_MODE);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (FIELD_GET(GENMASK(5, 5), ret)) {
> +		ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE,
> +						page == 0 ? 3 : 4);
> +		if (ret < 0)
> +			return ret;
> +
> +		ret = i2c_smbus_read_word_data(client, MFR_VR_MULTI_CONFIG);
> +		if (ret < 0)
> +			return ret;
> +
> +		if (FIELD_GET(GENMASK(5, 5), ret))
> +			data->vout_scale[page] = 2560;
> +		else
> +			data->vout_scale[page] = 5120;
> +	} else if (FIELD_GET(GENMASK(4, 4), ret)) {
> +		data->vout_scale[page] = 1;
> +	} else {
> +		data->vout_scale[page] = 512;
> +	}
> +
> +	return 0;
> +}
> +
> +static int mp2925_identify(struct i2c_client *client, struct pmbus_driver_info *info)
> +{
> +	int ret;
> +
> +	ret = mp2925_identify_vout_scale(client, info, 0);
> +	if (ret < 0)
> +		return ret;
> +
> +	return mp2925_identify_vout_scale(client, info, 1);
> +}
> +
> +static const struct pmbus_driver_info mp2925_info = {
> +	.pages = MP2925_PAGE_NUM,
> +	.format[PSC_VOLTAGE_IN] = linear,
> +	.format[PSC_CURRENT_IN] = linear,
> +	.format[PSC_CURRENT_OUT] = linear,
> +	.format[PSC_POWER] = linear,
> +	.format[PSC_TEMPERATURE] = linear,
> +	.format[PSC_VOLTAGE_OUT] = direct,
> +
> +	.m[PSC_VOLTAGE_OUT] = 1,
> +	.R[PSC_VOLTAGE_OUT] = 3,
> +	.b[PSC_VOLTAGE_OUT] = 0,
> +
> +	.func[0] = MP2925_RAIL1_FUNC,
> +	.func[1] = MP2925_RAIL2_FUNC,
> +	.read_word_data = mp2925_read_word_data,
> +	.read_byte_data = mp2925_read_byte_data,
> +	.write_word_data = mp2925_write_word_data,
> +	.identify = mp2925_identify,
> +};
> +
> +static int mp2925_probe(struct i2c_client *client)
> +{
> +	struct mp2925_data *data;
> +
> +	data = devm_kzalloc(&client->dev, sizeof(struct mp2925_data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	memcpy(&data->info, &mp2925_info, sizeof(mp2925_info));
> +
> +	return pmbus_do_probe(client, &data->info);
> +}
> +
> +static const struct i2c_device_id mp2925_id[] = {
> +	{"mp2925", 0},
> +	{"mp2929", 1},

I don't see where {0, 1} is used. If the chips do not require chip
specific handling, drop and just pass 0 for both chips. If they do,
use an enum.

Thanks,
Guenter

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