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Date: Mon, 13 May 2024 07:20:22 -0700
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Subject: Re: [PATCH] hwmon: add MP2891 driver
To: Noah Wang <noahwang.wang@outlook.com>, jdelvare@suse.com
Cc: linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org
References: <SEYPR04MB64825A740FDE7282B2FECEE2FAE22@SEYPR04MB6482.apcprd04.prod.outlook.com>
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On 5/12/24 22:52, Noah Wang wrote:
> This driver is designed for MPS VR controller mp2891. The input
> voltage, output voltage, input current, output current, input
> power, output power and temperature of per rail can be obtained
> from hwmon sysfs that the driver provided.
> 
> Signed-off-by: Noah Wang <noahwang.wang@outlook.com>
> ---
>   Documentation/hwmon/mp2891.rst |  95 +++++++++++++++

Needs to be added to index.rst.

>   drivers/hwmon/pmbus/Kconfig    |   9 ++
>   drivers/hwmon/pmbus/Makefile   |   1 +
>   drivers/hwmon/pmbus/mp2891.c   | 210 +++++++++++++++++++++++++++++++++
>   4 files changed, 315 insertions(+)
>   create mode 100644 Documentation/hwmon/mp2891.rst
>   create mode 100644 drivers/hwmon/pmbus/mp2891.c
> 
> diff --git a/Documentation/hwmon/mp2891.rst b/Documentation/hwmon/mp2891.rst
> new file mode 100644
> index 000000000..eaf73fe60
> --- /dev/null
> +++ b/Documentation/hwmon/mp2891.rst
> @@ -0,0 +1,95 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +Kernel driver mp2891
> +====================
> +
> +Supported chips:
> +
> +  * MPS mp2891
> +
> +    Prefix: 'mp2891'
> +
> +  * Datasheet
> +
> +    Publicly available at the MPS website : https://www.monolithicpower.com/en/mp2891.html

No, it isn't. It is not even accessible with an account (the provided "datasheet"
is a useless one-pager).

> +
> +Author:
> +
> +	Noah Wang <noahwang.wang@outlook.com>
> +
> +Description
> +-----------
> +
> +This driver implements support for Monolithic Power Systems, Inc. (MPS)
> +MP2891 Multi-phase Digital VR Controller.
> +
> +Device compliant with:
> +
> +- PMBus rev 1.3 interface.
> +
> +Device supports direct and linear format for reading input voltage,
> +output voltage, input currect, output current, input power, output
> +power, and temperature.
> +
> +The driver exports the following attributes via the 'sysfs' files
> +for input voltage:
> +
> +**in1_input**
> +
> +**in1_label**
> +
> +The driver provides the following attributes for output voltage:
> +
> +**in2_input**
> +
> +**in2_label**
> +
> +**in3_input**
> +
> +**in3_label**
> +
> +The driver provides the following attributes for input current:
> +
> +**curr1_input**
> +
> +**curr1_label**
> +
> +**curr2_input**
> +
> +**curr2_label**
> +
> +The driver provides the following attributes for output current:
> +
> +**curr3_input**
> +
> +**curr3_label**
> +
> +**curr4_input**
> +
> +**curr4_label**
> +
> +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**
> +
> +**temp2_input**
> diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
> index 557ae0c41..b8b6c7724 100644
> --- a/drivers/hwmon/pmbus/Kconfig
> +++ b/drivers/hwmon/pmbus/Kconfig
> @@ -361,6 +361,15 @@ config SENSORS_MP5990
>   	  This driver can also be built as a module. If so, the module will
>   	  be called mp5990.
> 
> +config SENSORS_MP2891
> +    tristate "MPS MP2891"
> +    help
> +      If you say yes here you get hardware monitoring support for MPS
> +      MP2891 Dual Loop Digital Multi-Phase Controller.
> +
> +      This driver can also be built as a module. If so, the module will
> +      be called mp2891.
> +
>   config SENSORS_MPQ7932_REGULATOR
>   	bool "Regulator support for MPQ7932"
>   	depends on SENSORS_MPQ7932 && REGULATOR
> diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
> index f14ecf03a..57b91c20e 100644
> --- a/drivers/hwmon/pmbus/Makefile
> +++ b/drivers/hwmon/pmbus/Makefile
> @@ -38,6 +38,7 @@ obj-$(CONFIG_SENSORS_MP2888)	+= mp2888.o
>   obj-$(CONFIG_SENSORS_MP2975)	+= mp2975.o
>   obj-$(CONFIG_SENSORS_MP5023)	+= mp5023.o
>   obj-$(CONFIG_SENSORS_MP5990)	+= mp5990.o
> +obj-$(CONFIG_SENSORS_MP2891)   += mp2891.o
>   obj-$(CONFIG_SENSORS_MPQ7932)	+= mpq7932.o
>   obj-$(CONFIG_SENSORS_MPQ8785)	+= mpq8785.o
>   obj-$(CONFIG_SENSORS_PLI1209BC)	+= pli1209bc.o
> diff --git a/drivers/hwmon/pmbus/mp2891.c b/drivers/hwmon/pmbus/mp2891.c
> new file mode 100644
> index 000000000..c98d9ec6b
> --- /dev/null
> +++ b/drivers/hwmon/pmbus/mp2891.c
> @@ -0,0 +1,210 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Hardware monitoring driver for MPS Multi-phase Digital VR Controllers(MP2891)
> + */
> +
> +#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, the register READ_PIN_EST(0x94),

Please use standard multi-line comments.

> + * MFR_VOUT_LOOP_CTRL(0xBD) and READ_IIN_EST(0x95) redefine
> + * the standard PMBUS register.

That doesn't explain the reason for using the _EST registers
instead of the standard registers.

> + */
> +#define MFR_VOUT_LOOP_CTRL      0xBD
> +#define READ_PIN_EST            0x94
> +#define READ_IIN_EST            0x95
> +
> +#define MP2891_PAGE_NUM			2
> +
> +#define MP2891_RAIL1_FUNC	(PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT | \
> +							PMBUS_HAVE_IOUT | PMBUS_HAVE_TEMP | \
> +							PMBUS_HAVE_POUT | PMBUS_HAVE_PIN | \
> +							PMBUS_HAVE_IIN | PMBUS_PHASE_VIRTUAL)
> +
> +#define MP2891_RAIL2_FUNC	(PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT | \
> +							PMBUS_HAVE_TEMP | PMBUS_HAVE_POUT | \
> +							PMBUS_HAVE_IIN | PMBUS_PHASE_VIRTUAL)

What is the point of PMBUS_PHASE_VIRTUAL ?

> +
> +struct mp2891_data {
> +	struct pmbus_driver_info info;
> +};
> +
> +#define to_mp2891_data(x) container_of(x, struct mp2891_data, info)
> +
Unused.

> +static int mp2891_read_byte_data(struct i2c_client *client, int page, int reg)
> +{
> +	int ret;
> +
> +	switch (reg) {
> +	case PMBUS_VOUT_MODE:
> +		ret = PB_VOUT_MODE_DIRECT;

Needs explanation.

> +		break;
> +	default:
> +		ret = -EINVAL;

No status registers ? I do not believe this is correct.

> +		break;
> +	}
> +
> +	return ret;
> +}
> +
> +static int mp2891_read_word_data(struct i2c_client *client, int page, int phase,
> +			      int reg)
> +{
> +	int ret;
> +
> +	switch (reg) {
> +	case PMBUS_READ_VIN:
> +	case PMBUS_READ_IOUT:
> +	case PMBUS_READ_POUT:
> +	case PMBUS_READ_VOUT:
> +	case PMBUS_READ_TEMPERATURE_1:
> +		ret = pmbus_read_word_data(client, page, phase, reg);

Use
		return -ENODATA;
instead.

> +		break;
> +	case PMBUS_READ_IIN:
> +		ret = pmbus_read_word_data(client, page, phase, READ_IIN_EST);
> +		break;
> +	case PMBUS_READ_PIN:
> +		ret = pmbus_read_word_data(client, page, phase, READ_PIN_EST);

This needs an explanation. Why not use standard READ_IIN and READ_PIN ?

> +		break;
> +	default:
> +		ret = -EINVAL;

No limit registers ? That seems extremely unlikely.


Given that you are essentially claiming that the chip would support
almost no standard registers, I'll need to see the datasheet to confirm.

> +		break;
> +	}
> +
> +	return ret;
> +}
> +
> +static int
> +mp2891_identify_vout_scale(struct i2c_client *client, struct mp2891_data *data,
> +							u32 reg, int page)
> +{
> +	int ret;
> +
> +	ret = i2c_smbus_write_byte_data(client, PMBUS_PAGE, page);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = i2c_smbus_read_word_data(client, reg);
> +	if (ret < 0)
> +		return ret;
> +
> +	/*
> +	 * Obtain vout scale from the register MFR_VOUT_LOOP_CTRL, bits 15-14,bit 13.
> +	 * If MFR_VOUT_LOOP_CTRL[13] = 1, the vout scale is below:
> +	 * 2.5mV/LSB
> +	 * If MFR_VOUT_LOOP_CTRL[13] = 0, the vout scale is decided by
> +	 * MFR_VOUT_LOOP_CTRL[15:14]:
> +	 * 00b - 6.25mV/LSB, 01b - 5mV/LSB, 10b - 2mV/LSB, 11b - 1mV
> +	 */
> +	if (ret & GENMASK(13, 13)) {
> +		data->info.m[PSC_VOLTAGE_OUT] = 4;
> +		data->info.R[PSC_VOLTAGE_OUT] = -1;
> +		data->info.b[PSC_VOLTAGE_OUT] = 0;
> +	} else {
> +		ret = (ret & GENMASK(15, 14)) >> 14;

Why not FIELD_GET() ?

> +		if (ret == 0) {
> +			data->info.m[PSC_VOLTAGE_OUT] = 16;
> +			data->info.R[PSC_VOLTAGE_OUT] = -2;
> +			data->info.b[PSC_VOLTAGE_OUT] = 0;
> +		} else if (ret == 1) {
> +			data->info.m[PSC_VOLTAGE_OUT] = 2;
> +			data->info.R[PSC_VOLTAGE_OUT] = -1;
> +			data->info.b[PSC_VOLTAGE_OUT] = 0;
> +		} else if (ret == 2) {
> +			data->info.m[PSC_VOLTAGE_OUT] = 5;
> +			data->info.R[PSC_VOLTAGE_OUT] = -1;
> +			data->info.b[PSC_VOLTAGE_OUT] = 0;
> +		} else {
> +			data->info.m[PSC_VOLTAGE_OUT] = 1;
> +			data->info.R[PSC_VOLTAGE_OUT] = 0;
> +			data->info.b[PSC_VOLTAGE_OUT] = 0;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static int
> +mp2891_identify_rails_vout_scale(struct i2c_client *client, struct mp2891_data *data)
> +{
> +	int ret;
> +
> +	/* Identify vout scale from register  MFR_VOUT_LOOP_CTRL. */

Useless comment.

> +	/* Identify vout scale for rail 1. */
> +	ret = mp2891_identify_vout_scale(client, data, MFR_VOUT_LOOP_CTRL, 0);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Identify vout scale for rail 2. */
> +	ret = mp2891_identify_vout_scale(client, data, MFR_VOUT_LOOP_CTRL, 1);

Passing the register to this function is useless. Just use the register directly
in mp2891_identify_vout_scale().

> +
> +	return ret;
> +}
> +
> +static struct pmbus_driver_info mp2891_info = {
> +	.pages = MP2891_PAGE_NUM,
> +	.format[PSC_VOLTAGE_IN] = linear,
> +	.format[PSC_CURRENT_IN] = linear,
> +	.format[PSC_CURRENT_OUT] = linear,
> +	.format[PSC_TEMPERATURE] = linear,
> +	.format[PSC_POWER] = linear,
> +	.format[PSC_VOLTAGE_OUT] = direct,
> +
> +	.func[0] = MP2891_RAIL1_FUNC,
> +	.func[1] = MP2891_RAIL2_FUNC,
> +	.read_word_data = mp2891_read_word_data,
> +	.read_byte_data = mp2891_read_byte_data,
> +};
> +
> +static int mp2891_probe(struct i2c_client *client)
> +{
> +	struct pmbus_driver_info *info;
> +	struct mp2891_data *data;
> +	int ret;
> +
> +	data = devm_kzalloc(&client->dev, sizeof(struct mp2891_data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	memcpy(&data->info, &mp2891_info, sizeof(*info));
> +	info = &data->info;
> +
> +	/* Identify vout scale per rail. */
> +	ret = mp2891_identify_rails_vout_scale(client, data);
> +	if (ret < 0)
> +		return ret;
> +

Why not use the identify() callback instead ?

> +	return pmbus_do_probe(client, info);
> +}
> +
> +static const struct i2c_device_id mp2891_id[] = {
> +	{"mp2891", 0},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, mp2891_id);
> +
> +static const struct of_device_id __maybe_unused mp2891_of_match[] = {
> +	{.compatible = "mps,mp2891"},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, mp2891_of_match);
> +
> +static struct i2c_driver mp2891_driver = {
> +	.driver = {
> +		.name = "mp2891",
> +		.of_match_table = mp2891_of_match,
> +	},
> +	.probe = mp2891_probe,
> +	.id_table = mp2891_id,
> +};
> +
> +module_i2c_driver(mp2891_driver);
> +
> +MODULE_AUTHOR("Noah Wang <noahwang.wang@outlook.com>");
> +MODULE_DESCRIPTION("PMBus driver for MPS MP2891 device");

drop "device"

> +MODULE_LICENSE("GPL");
> +MODULE_IMPORT_NS(PMBUS);
> --
> 2.25.1
>