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Message-ID: <48471efc-8ea2-41f6-9fd7-0d4c33806ab3@roeck-us.net>
Date: Thu, 18 Dec 2025 09:49:49 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Yuxi Wang <Yuxi.Wang@...olithicpower.com>
Cc: corbet@....net, robh@...nel.org, krzk+dt@...nel.org,
conor+dt@...nel.org, wyx137120466@...il.com,
linux-hwmon@...r.kernel.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 RESEND 2/2] hwmon: add mp5926 driver
On Mon, Dec 15, 2025 at 10:25:05AM +0800, Yuxi Wang wrote:
> Add support for mps mp5926.
>
> Signed-off-by: Yuxi Wang <Yuxi.Wang@...olithicpower.com>
> ---
> Documentation/hwmon/index.rst | 1 +
> Documentation/hwmon/mp5926.rst | 92 ++++++++++++++++
> MAINTAINERS | 7 ++
> drivers/hwmon/pmbus/Kconfig | 9 ++
> drivers/hwmon/pmbus/Makefile | 1 +
> drivers/hwmon/pmbus/mp5926.c | 190 +++++++++++++++++++++++++++++++++
> 6 files changed, 300 insertions(+)
> create mode 100644 Documentation/hwmon/mp5926.rst
> create mode 100644 drivers/hwmon/pmbus/mp5926.c
>
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index 85d7a686883e..6181c3f62177 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -185,6 +185,7 @@ Hardware Monitoring Kernel Drivers
> mp2993
> mp5023
> mp5920
> + mp5926
> mp5990
> mp9941
> mp9945
> diff --git a/Documentation/hwmon/mp5926.rst b/Documentation/hwmon/mp5926.rst
> new file mode 100644
> index 000000000000..4b64a7e24ae6
> --- /dev/null
> +++ b/Documentation/hwmon/mp5926.rst
> @@ -0,0 +1,92 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +Kernel driver mp5926
> +====================
> +
> +Supported chips:
> +
> + * MPS mp5926
> +
> + Prefix: 'mp5926'
> +
> + * Datasheet
> + https://www.monolithicpower.com/en/
> +
> +Author:
> +
> + Yuxi Wang <Yuxi.Wang@...olithicpower.com>
> +
> +Description
> +-----------
> +
> +This driver implements support for Monolithic Power Systems, Inc. (MPS)
> +MP5926 Hot-Swap 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**
> +
> +The driver provides the following attributes for output voltage:
> +
> +**in2_input**
> +
> +**in2_label**
> +
> +**in2_lcrit**
> +
> +**in2_lcrit_alarm**
> +
> +**in2_rated_max**
> +
> +**in2_rated_min**
> +
> +The driver provides the following attributes for input current:
> +
> +**curr1_input**
> +
> +**curr1_label**
> +
> +**curr1_max**
> +
> +**curr1_max_alarm**
> +
> +The driver provides the following attributes for output current:
> +
> +**curr2_input**
> +
> +**curr2_label**
> +
> +The driver provides the following attributes for input power:
> +
> +**power1_input**
> +
> +**power1_label**
> +
> +The driver provides the following attributes for output power:
> +
> +**power2_input**
> +
> +**power2_label**
> +
> +The driver provides the following attributes for temperature:
> +
> +**temp1_input**
> +
> +**temp1_crit**
> +
> +**temp1_crit_alarm**
> +
> +**temp1_max**
> +
> +**temp1_max_alarm**
> diff --git a/MAINTAINERS b/MAINTAINERS
> index d701a4d5b00e..fea710aab535 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -17708,6 +17708,13 @@ S: Maintained
> F: Documentation/hwmon/mp2993.rst
> F: drivers/hwmon/pmbus/mp2993.c
>
> +MPS MP5926 DRIVER
> +M: Yuxi Wang <Yuxi.Wang@...olithicpower.com>
> +L: linux-hwmon@...r.kernel.org
> +S: Maintained
> +F: Documentation/hwmon/mp5926.rst
> +F: drivers/hwmon/pmbus/mp5926.c
> +
> MPS MP9941 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 f3fb94cebf1a..d0aa460abdc9 100644
> --- a/drivers/hwmon/pmbus/Kconfig
> +++ b/drivers/hwmon/pmbus/Kconfig
> @@ -472,6 +472,15 @@ config SENSORS_MP5920
> This driver can also be built as a module. If so, the module will
> be called mp5920.
>
> +config SENSORS_MP5926
> + tristate "MPS MP5926"
> + help
> + If you say yes here you get hardware monitoring support for Monolithic
> + MP5926.
> +
> + This driver can also be built as a module. If so, the module will
> + be called mp5926.
> +
> config SENSORS_MP5990
> tristate "MPS MP5990"
> help
> diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
> index 349a89b6d92e..75ec4956ca8d 100644
> --- a/drivers/hwmon/pmbus/Makefile
> +++ b/drivers/hwmon/pmbus/Makefile
> @@ -47,6 +47,7 @@ obj-$(CONFIG_SENSORS_MP2975) += mp2975.o
> obj-$(CONFIG_SENSORS_MP2993) += mp2993.o
> obj-$(CONFIG_SENSORS_MP5023) += mp5023.o
> obj-$(CONFIG_SENSORS_MP5920) += mp5920.o
> +obj-$(CONFIG_SENSORS_MP5926) += mp5926.o
> obj-$(CONFIG_SENSORS_MP5990) += mp5990.o
> obj-$(CONFIG_SENSORS_MP9941) += mp9941.o
> obj-$(CONFIG_SENSORS_MP9945) += mp9945.o
> diff --git a/drivers/hwmon/pmbus/mp5926.c b/drivers/hwmon/pmbus/mp5926.c
> new file mode 100644
> index 000000000000..3122854b07f8
> --- /dev/null
> +++ b/drivers/hwmon/pmbus/mp5926.c
> @@ -0,0 +1,190 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +//
> +// mp5926.c - pmbus driver for mps mp5926
> +//
> +// Copyright 2025 Monolithic Power Systems, Inc
> +//
> +// Author: Yuxi Wang <Yuxi.Wang@...olithicpower.com>
> +
> +#include <linux/bitfield.h>
> +#include <linux/bits.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/pmbus.h>
> +#include "pmbus.h"
> +
> +#define PAGE 0x01
> +#define EFUSE_CFG 0xCF
> +#define I_SCALE_SEL 0xC6
> +#define MP5926_FUNC (PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT | \
> + PMBUS_HAVE_IIN | PMBUS_HAVE_PIN | \
> + PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_INPUT | \
> + PMBUS_HAVE_STATUS_TEMP | PMBUS_HAVE_STATUS_VOUT)
> +
> +struct mp5926_data {
> + struct pmbus_driver_info info;
> + u8 vout_mode;
> + u8 vout_linear_exponent;
> +};
> +
> +#define to_mp5926_data(x) container_of(x, struct mp5926_data, info)
> +
> +static int mp5926_read_byte_data(struct i2c_client *client, int page,
> + int reg)
> +{
> + const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
> + struct mp5926_data *data = to_mp5926_data(info);
> + int ret;
> +
> + switch (reg) {
> + case PMBUS_VOUT_MODE:
> + if (data->vout_mode == linear) {
> + /*
> + * The VOUT format used by the chip is linear11,
> + * not linear16. Report that VOUT is in linear mode
> + * and return exponent value extracted while probing
> + * the chip.
> + */
> + return data->vout_linear_exponent;
> + } else {
else after return is not needed.
> + return PB_VOUT_MODE_DIRECT;
> + }
> + break;
and neither is a break after unconditional return.
> + default:
> + ret = -ENODATA;
> + break;
> + }
> + return ret;
> +}
> +
> +static int mp5926_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 mp5926_data *data = to_mp5926_data(info);
> + int ret;
> + s32 mantissa;
> +
> + switch (reg) {
> + case PMBUS_READ_VOUT:
> + ret = pmbus_read_word_data(client, page, phase, reg);
> + if (ret < 0)
> + return ret;
> + /*
> + * Because the VOUT format used by the chip is linear11 and not
> + * linear16, we disregard bits[15:11]. The exponent is reported
> + * as part of the VOUT_MODE command.
> + */
> + if (data->vout_mode == linear) {
> + mantissa = ((s16)((ret & 0x7ff) << 5)) >> 5;
> + ret = mantissa;
The extra 'mantissa' variable is really unnecessary.
ret = ((s16)((ret & 0x7ff) << 5)) >> 5;
or even better sign_extend32() would be sufficient.
> + }
> + break;
> + default:
> + ret = -ENODATA;
> + break;
> + }
> + return ret;
> +}
> +
> +static struct pmbus_driver_info mp5926_info = {
> + .pages = PAGE,
> + .format[PSC_VOLTAGE_IN] = direct,
> + .format[PSC_CURRENT_IN] = direct,
> + .format[PSC_VOLTAGE_OUT] = direct,
> + .format[PSC_TEMPERATURE] = direct,
> + .format[PSC_POWER] = direct,
> +
> + .m[PSC_VOLTAGE_IN] = 16,
> + .b[PSC_VOLTAGE_IN] = 0,
> + .R[PSC_VOLTAGE_IN] = 0,
> +
> + .m[PSC_CURRENT_IN] = 16,
> + .b[PSC_CURRENT_IN] = 0,
> + .R[PSC_CURRENT_IN] = 0,
> +
> + .m[PSC_VOLTAGE_OUT] = 16,
> + .b[PSC_VOLTAGE_OUT] = 0,
> + .R[PSC_VOLTAGE_OUT] = 0,
> +
> + .m[PSC_TEMPERATURE] = 4,
> + .b[PSC_TEMPERATURE] = 0,
> + .R[PSC_TEMPERATURE] = 0,
> +
> + .m[PSC_POWER] = 25,
> + .b[PSC_POWER] = 0,
> + .R[PSC_POWER] = -2,
> +
> + .read_word_data = mp5926_read_word_data,
> + .read_byte_data = mp5926_read_byte_data,
> + .func[0] = MP5926_FUNC,
> +};
> +
> +static int mp5926_probe(struct i2c_client *client)
> +{
> + struct mp5926_data *data;
> + struct pmbus_driver_info *info;
> + int ret;
> +
> + data = devm_kzalloc(&client->dev, sizeof(struct mp5926_data),
> + GFP_KERNEL);
> + if (!data)
> + return -ENOMEM;
> +
> + memcpy(&data->info, &mp5926_info, sizeof(*info));
> + info = &data->info;
> + ret = i2c_smbus_read_word_data(client, EFUSE_CFG);
> + if (ret < 0)
> + return ret;
> + if (ret & BIT(12)) {
> + data->vout_mode = linear;
> + data->info.format[PSC_VOLTAGE_IN] = linear;
> + data->info.format[PSC_CURRENT_IN] = linear;
> + data->info.format[PSC_VOLTAGE_OUT] = linear;
> + data->info.format[PSC_TEMPERATURE] = linear;
> + data->info.format[PSC_POWER] = linear;
> + ret = i2c_smbus_read_word_data(client, PMBUS_READ_VOUT);
> + if (ret < 0) {
> + dev_err(&client->dev, "Can't get vout exponent.");
> + return ret;
dev_err_probe() would be useful here.
> + }
> + data->vout_linear_exponent = (u8)((ret >> 11) & 0x1f);
> + } else {
> + data->vout_mode = direct;
> + ret = i2c_smbus_read_word_data(client, I_SCALE_SEL);
> + if (ret < 0)
> + return ret;
> + if (ret & BIT(6))
> + data->info.m[PSC_CURRENT_IN] = 4;
> + }
> +
> + return pmbus_do_probe(client, info);
> +}
> +
> +static const struct i2c_device_id mp5926_id[] = {
> + { "mp5926", 0 },
> + {}
> +};
> +MODULE_DEVICE_TABLE(i2c, mp5926_id);
> +
> +static const struct of_device_id mp5926_of_match[] = {
> + { .compatible = "mps,mp5926" },
> + {}
> +};
> +MODULE_DEVICE_TABLE(of, mp5926_of_match);
> +
> +static struct i2c_driver mp5926_driver = {
> + .probe = mp5926_probe,
> + .driver = {
> + .name = "mp5926",
> + .of_match_table = mp5926_of_match,
> + },
> + .id_table = mp5926_id,
> +};
> +
> +module_i2c_driver(mp5926_driver);
> +MODULE_AUTHOR("Yuxi Wang <Yuxi.Wang@...olithicpower.com>");
> +MODULE_DESCRIPTION("MPS MP5926 pmbus driver");
> +MODULE_LICENSE("GPL");
> +MODULE_IMPORT_NS("PMBUS");
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