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Sender: Guenter Roeck <groeck7@gmail.com>
Message-ID: <c74beccd-26ea-4e63-906b-bd5508465cbc@roeck-us.net>
Date:   Fri, 3 Nov 2023 07:35:51 -0700
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User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v1 2/2] hwmon: (pmbus) Add support for MPS Multi-phase
 mp5990
Content-Language: en-US
To:     Peter Yin <peteryin.openbmc@gmail.com>, patrick@stwcx.xyz,
        Jean Delvare <jdelvare@suse.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Jonathan Corbet <corbet@lwn.net>, linux-hwmon@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org
References: <20231103080128.1204218-1-peteryin.openbmc@gmail.com>
 <20231103080128.1204218-3-peteryin.openbmc@gmail.com>
From:   Guenter Roeck <linux@roeck-us.net>
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In-Reply-To: <20231103080128.1204218-3-peteryin.openbmc@gmail.com>
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Precedence: bulk

On 11/3/23 01:01, Peter Yin wrote:
> Add support for mp5990 device from Monolithic Power Systems, Inc. (MPS)
> vendor. This is a Hot-Swap Controller.
> 
> Signed-off-by: Peter Yin <peteryin.openbmc@gmail.com>
> ---
>   Documentation/hwmon/index.rst  |  1 +
>   Documentation/hwmon/mp5990.rst | 84 +++++++++++++++++++++++++++++++
>   drivers/hwmon/pmbus/Kconfig    |  9 ++++
>   drivers/hwmon/pmbus/Makefile   |  1 +
>   drivers/hwmon/pmbus/mp5990.c   | 90 ++++++++++++++++++++++++++++++++++
>   5 files changed, 185 insertions(+)
>   create mode 100644 Documentation/hwmon/mp5990.rst
>   create mode 100644 drivers/hwmon/pmbus/mp5990.c
> 
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index 042e1cf9501b..8c70e10fc795 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -157,6 +157,7 @@ Hardware Monitoring Kernel Drivers
>      mp2888
>      mp2975
>      mp5023
> +   mp5990
>      nct6683
>      nct6775
>      nct7802
> diff --git a/Documentation/hwmon/mp5990.rst b/Documentation/hwmon/mp5990.rst
> new file mode 100644
> index 000000000000..8fc4e388ff7b
> --- /dev/null
> +++ b/Documentation/hwmon/mp5990.rst
> @@ -0,0 +1,84 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +Kernel driver mp5990
> +====================
> +
> +Supported chips:
> +
> +  * MPS MP5990
> +
> +    Prefix: 'mp5990'
> +
> +  * Datasheet
> +
> +    Publicly available at the MPS website : https://www.monolithicpower.com/en/mp5990.html
> +
> +Author:
> +
> +	Peter Yin <peteryin.openbmc@gmail.com>
> +
> +Description
> +-----------
> +
> +This driver implements support for Monolithic Power Systems, Inc. (MPS)
> +MP5990 Hot-Swap Controller.
> +
> +Device complaint with:

compliant

> +
> +- PMBus rev 1.3 interface.
> +
> +Device supports direct format for reading input voltage, output voltage,
> +output current, input power and temperature.
> +
> +The driver exports the following attributes via the 'sysfs' files
> +for input voltage:
> +
> +**in1_input**
> +
> +**in1_label**
> +
> +**in1_max**
> +
> +**in1_max_alarm**
> +
> +**in1_min**
> +
> +**in1_min_alarm**
> +
> +The driver provides the following attributes for output voltage:
> +
> +**in2_input**
> +
> +**in2_label**
> +
> +**in2_alarm**
> +
> +The driver provides the following attributes for output current:
> +
> +**curr1_input**
> +
> +**curr1_label**
> +
> +**curr1_alarm**
> +
> +**curr1_max**
> +
> +The driver provides the following attributes for input power:
> +
> +**power1_input**
> +
> +**power1_label**
> +
> +**power1_alarm**
> +
> +The driver provides the following attributes for temperature:
> +
> +**temp1_input**
> +
> +**temp1_max**
> +
> +**temp1_max_alarm**
> +
> +**temp1_crit**
> +
> +**temp1_crit_alarm**
> diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
> index 270b6336b76d..65a116f7744d 100644
> --- a/drivers/hwmon/pmbus/Kconfig
> +++ b/drivers/hwmon/pmbus/Kconfig
> @@ -326,6 +326,15 @@ config SENSORS_MP5023
>   	  This driver can also be built as a module. If so, the module will
>   	  be called mp5023.
>   
> +config SENSORS_MP5990
> +	tristate "MPS MP5990"
> +	help
> +	  If you say yes here you get hardware monitoring support for MPS
> +	  MP5990.
> +
> +	  This driver can also be built as a module. If so, the module will
> +	  be called mp5990.
> +
>   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 84ee960a6c2d..212d9ca0acc9 100644
> --- a/drivers/hwmon/pmbus/Makefile
> +++ b/drivers/hwmon/pmbus/Makefile
> @@ -35,6 +35,7 @@ obj-$(CONFIG_SENSORS_MAX8688)	+= max8688.o
>   obj-$(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_MPQ7932)	+= mpq7932.o
>   obj-$(CONFIG_SENSORS_PLI1209BC)	+= pli1209bc.o
>   obj-$(CONFIG_SENSORS_PM6764TR)	+= pm6764tr.o
> diff --git a/drivers/hwmon/pmbus/mp5990.c b/drivers/hwmon/pmbus/mp5990.c
> new file mode 100644
> index 000000000000..c3b31af9f750
> --- /dev/null
> +++ b/drivers/hwmon/pmbus/mp5990.c
> @@ -0,0 +1,90 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Driver for MPS MP5990 Hot-Swap Controller
> + */
> +
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/pmbus.h>
> +#include "pmbus.h"
> +
> +static int mp5990_read_byte_data(struct i2c_client *client, int page, int reg)
> +{
> +	switch (reg) {
> +	case PMBUS_VOUT_MODE:
> +		/*
> +		  Enforce VOUT direct format, C4h reg BIT9
> +		  default val is not match vout format
> +		 */

/*
  * Please use proper multi-line comments. Also, the problem here is that the
  * chip does not support the VOUT_MODE command, which should be mentioned.
  *
  * On top of that, overwriting PMBUS_VOUT_MODE result from the chip is only
  * necessary if the chip does not return an error when reading the value.
  * If that is the case, it should be mentioned in the comment. The above
  * does not explain why this would be needed, even if the command is not
  * (officially) supported by the chip. What does it return that requires
  * an overwrite ?
  */

> +		return PB_VOUT_MODE_DIRECT;
> +	default:
> +		return -ENODATA;
> +	}
> +}
> +
> +static struct pmbus_driver_info mp5990_info = {
> +	.pages = 1,
> +	.format[PSC_VOLTAGE_IN] = direct,
> +	.format[PSC_VOLTAGE_OUT] = direct,
> +	.format[PSC_CURRENT_OUT] = direct,
> +	.format[PSC_POWER] = direct,
> +	.format[PSC_TEMPERATURE] = direct,
> +	.m[PSC_VOLTAGE_IN] = 32,
> +	.b[PSC_VOLTAGE_IN] = 0,
> +	.R[PSC_VOLTAGE_IN] = 0,
> +	.m[PSC_VOLTAGE_OUT] = 32,
> +	.b[PSC_VOLTAGE_OUT] = 0,
> +	.R[PSC_VOLTAGE_OUT] = 0,
> +	.m[PSC_CURRENT_OUT] = 16,
> +	.b[PSC_CURRENT_OUT] = 0,
> +	.R[PSC_CURRENT_OUT] = 0,
> +	.m[PSC_POWER] = 1,
> +	.b[PSC_POWER] = 0,
> +	.R[PSC_POWER] = 0,
> +	.m[PSC_TEMPERATURE] = 1,
> +	.b[PSC_TEMPERATURE] = 0,
> +	.R[PSC_TEMPERATURE] = 0,
> +	.func[0] =
> +		PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT | PMBUS_HAVE_PIN |
> +		PMBUS_HAVE_TEMP | PMBUS_HAVE_IOUT |
> +		PMBUS_HAVE_STATUS_INPUT | PMBUS_HAVE_STATUS_TEMP,
> +	.read_byte_data = mp5990_read_byte_data,
> +};
> +
> +static int mp5990_probe(struct i2c_client *client)
> +{
> +	int ret;
> +
> +	ret = i2c_smbus_write_byte_data(client, PMBUS_VOUT_MODE,
> +					PB_VOUT_MODE_DIRECT);

According to the datasheet, the chip does not support the VOUT_MODE
command. Supposedly, direct vs. linear mode is selected with bit 9
of EFUSE_CFG. Even if the chip happens to "silently" support the command,
the official command should be used to select the chip mode.

Next question: Why use direct mode ? Linear mode is supported and would
be much more flexible.

> +	if (ret < 0)
> +		return ret;
> +	return pmbus_do_probe(client, &mp5990_info);
> +}
> +
> +static const struct of_device_id mp5990_of_match[] = {
> +	{ .compatible = "mps,mp5990" },
> +	{}
> +};
> +
> +static const struct i2c_device_id mp5990_id[] = {
> +	{"mp5990", 0},
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(i2c, mp5990_id);
> +
> +static struct i2c_driver mp5990_driver = {
> +	.driver = {
> +		   .name = "mp5990",
> +		   .of_match_table = of_match_ptr(mp5990_of_match),

Using of_match_ptr() will result in a build failure if CONFIG_OF=n.

> +	},
> +	.probe = mp5990_probe,
> +	.id_table = mp5990_id,
> +};
> +module_i2c_driver(mp5990_driver);
> +
> +MODULE_AUTHOR("Peter Yin <peter.yin@quantatw.com>");
> +MODULE_DESCRIPTION("PMBus driver for MP5990 HSC");
> +MODULE_LICENSE("GPL");
> +MODULE_IMPORT_NS(PMBUS);