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Sender: Guenter Roeck <groeck7@gmail.com>
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Date:   Fri, 11 Feb 2022 11:40:47 -0800
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To:     Marcello Sylvester Bauer <sylv@sylv.io>,
        linux-hwmon@vger.kernel.org
Cc:     Jean Delvare <jdelvare@suse.com>, linux-kernel@vger.kernel.org
References: <cover.1644597670.git.sylv@sylv.io>
 <e4d83b95cfb0cc0c6acb65bd1263cf0131b6ce51.1644597670.git.sylv@sylv.io>
From:   Guenter Roeck <linux@roeck-us.net>
Subject: Re: [PATCH v1 3/4] pmbus: Add support for pli1209bc
In-Reply-To: <e4d83b95cfb0cc0c6acb65bd1263cf0131b6ce51.1644597670.git.sylv@sylv.io>
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On 2/11/22 09:17, Marcello Sylvester Bauer wrote:
> PLI1209BC is a Digital Supervisor from Vicor Corporation.
> 
> Signed-off-by: Marcello Sylvester Bauer <sylv@sylv.io>
> ---
>   Documentation/hwmon/pli1209bc.rst |  73 +++++++++++++++++++++
>   drivers/hwmon/pmbus/Kconfig       |   9 +++
>   drivers/hwmon/pmbus/Makefile      |   1 +
>   drivers/hwmon/pmbus/pli1209bc.c   | 104 ++++++++++++++++++++++++++++++
>   4 files changed, 187 insertions(+)
>   create mode 100644 Documentation/hwmon/pli1209bc.rst
>   create mode 100644 drivers/hwmon/pmbus/pli1209bc.c
> 
> diff --git a/Documentation/hwmon/pli1209bc.rst b/Documentation/hwmon/pli1209bc.rst
> new file mode 100644
> index 000000000000..a3f686d03cf2
> --- /dev/null
> +++ b/Documentation/hwmon/pli1209bc.rst
> @@ -0,0 +1,73 @@
> +Kernel driver pli1209bc
> +=======================
> +
> +Supported chips:
> +
> +  * Digital Supervisor PLI1209BC
> +
> +    Prefix: 'pli1209bc'
> +
> +    Addresses scanned: 0x50 - 0x5F
> +
> +    Datasheet: https://www.vicorpower.com/documents/datasheets/ds-PLI1209BCxyzz-VICOR.pdf
> +
> +Authors:
> +    - Marcello Sylvester Bauer <sylv@sylv.io>
> +
> +Description
> +-----------
> +
> +The Vicor PLI1209BC is an isolated digital power system supervisor thatprovides
> +a communication interface between a host processor and one Bus Converter Module
> +(BCM). The PLI communicates with a system controller via a PMBus compatible
> +interface over an isolated UART interface. Through the PLI, the host processor
> +can configure, set protection limits, and monitor the BCM.
> +
> +Sysfs entries
> +-------------
> +
> +======================= ========================================================
> +in1_label		"vin2"
> +in1_input		Input voltage.
> +in1_rated_min		Minimum rated input voltage.
> +in1_rated_max		Maximum rated input voltage.
> +in1_max			Maximum input voltage.
> +in1_max_alarm		Input voltage high alarm.
> +in1_crit		Critical input voltage.
> +in1_crit_alarm		Input voltage critical alarm.
> +
> +in2_label		"vout2"
> +in2_input		Output voltage.
> +in2_rated_min		Minimum rated output voltage.
> +in2_rated_max		Maximum rated output voltage.
> +in2_alarm		Output voltage alarm
> +
> +curr1_label		"iin2"
> +curr1_input		Input current.
> +curr1_max		Maximum input current.
> +curr1_max_alarm		Maximum input current high alarm.
> +curr1_crit		Critical input current.
> +curr1_crit_alarm	Input current critical alarm.
> +
> +curr2_label		"iout2"
> +curr2_input		Output current.
> +curr2_crit		Critical output current.
> +curr2_crit_alarm	Output current critical alarm.
> +curr2_max		Maximum output current.
> +curr2_max_alarm		Output current high alarm.
> +
> +power1_label		"pin2"
> +power1_input		Input power.
> +power1_alarm		Input power alarm.
> +
> +power2_label		"pout2"
> +power2_input		Output power.
> +power2_rated_max	Maximum rated output power.
> +
> +temp1_input		Die temperature.
> +temp1_alarm		Die temperature alarm.
> +temp1_max		Maximum die temperature.
> +temp1_max_alarm		Die temperature high alarm.
> +temp1_crit		Critical die temperature.
> +temp1_crit_alarm	Die temperature critical alarm.
> +======================= ========================================================
> diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
> index c96f7b7338bd..831db423bea0 100644
> --- a/drivers/hwmon/pmbus/Kconfig
> +++ b/drivers/hwmon/pmbus/Kconfig
> @@ -310,6 +310,15 @@ config SENSORS_PIM4328
>   	  This driver can also be built as a module. If so, the module will
>   	  be called pim4328.
>   
> +config SENSORS_PLI1209BC
> +	tristate "Vicor PLI1209BC"
> +	help
> +	  If you say yes here you get hardware monitoring support for Vicor
> +	  PLI1209BC Digital Supervisor.
> +
> +	  This driver can also be built as a module. If so, the module will
> +	  be called pli1209bc.
> +
>   config SENSORS_PM6764TR
>   	tristate "ST PM6764TR"
>   	help
> diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
> index e5935f70c9e0..7ce74e3b8552 100644
> --- a/drivers/hwmon/pmbus/Makefile
> +++ b/drivers/hwmon/pmbus/Makefile
> @@ -34,6 +34,7 @@ obj-$(CONFIG_SENSORS_MP2888)	+= mp2888.o
>   obj-$(CONFIG_SENSORS_MP2975)	+= mp2975.o
>   obj-$(CONFIG_SENSORS_MP5023)	+= mp5023.o
>   obj-$(CONFIG_SENSORS_PM6764TR)	+= pm6764tr.o
> +obj-$(CONFIG_SENSORS_PLI1209BC)	+= pli1209bc.o
>   obj-$(CONFIG_SENSORS_PXE1610)	+= pxe1610.o
>   obj-$(CONFIG_SENSORS_Q54SJ108A2)	+= q54sj108a2.o
>   obj-$(CONFIG_SENSORS_STPDDC60)	+= stpddc60.o
> diff --git a/drivers/hwmon/pmbus/pli1209bc.c b/drivers/hwmon/pmbus/pli1209bc.c
> new file mode 100644
> index 000000000000..da345eb105fd
> --- /dev/null
> +++ b/drivers/hwmon/pmbus/pli1209bc.c
> @@ -0,0 +1,104 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Hardware monitoring driver for Vicor PLI1209BC Digital Supervisor
> + *
> + * Copyright (c) 2022 9elements GmbH
> + */
> +
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/pmbus.h>
> +#include "pmbus.h"
> +
> +/*
> + * The capability command is only supported at page 0. Probing the device while
> + * the page register is set to 1 will falsely enable PEC support. Disable
> + * capability probing accordingly, since the PLI1209BC does not have any
> + * additional capabilities.
> + */
> +static struct pmbus_platform_data pli1209bc_plat_data = {
> +	.flags = PMBUS_NO_CAPABILITY,
> +};
> +
> +static int pli1209bc_read_word_data(struct i2c_client *client, int page,
> +				    int phase, int reg)
> +{
> +	int data;
> +
> +	switch (reg) {
> +	/* PMBUS_READ_PIN uses a direct format with R=1 */
> +	case PMBUS_READ_PIN:
> +		data = pmbus_read_word_data(client, page, phase, reg);
> +		if (data < 0)
> +			return data;
> +		return div_s64(data + 5LL, 10L);

This results in a loss of precision. I think it would be better to avoid that
and instead model the output power as direct format with R=1, and multiply
register values reported for PMBUS_READ_POUT with 10.

> +	default:
> +		return -ENODATA;
> +	}
> +}
> +
> +static struct pmbus_driver_info pli1209bc_info = {
> +	.pages = 2,
> +	.format[PSC_VOLTAGE_IN] = direct,
> +	.format[PSC_VOLTAGE_OUT] = direct,
> +	.format[PSC_CURRENT_IN] = direct,
> +	.format[PSC_CURRENT_OUT] = direct,
> +	.format[PSC_POWER] = linear,
> +	.format[PSC_TEMPERATURE] = linear,

Those look like direct values to me. Linear would mean there is a
mantissa and an exponent, but I don't see that in the datasheet.
Please clarify; we don't want to have power values of 1024 and
above show up as negative numbers.

> +	.m[PSC_VOLTAGE_IN] = 1,
> +	.b[PSC_VOLTAGE_IN] = 0,
> +	.R[PSC_VOLTAGE_IN] = 1,
> +	.m[PSC_VOLTAGE_OUT] = 1,
> +	.b[PSC_VOLTAGE_OUT] = 0,
> +	.R[PSC_VOLTAGE_OUT] = 1,
> +	.m[PSC_CURRENT_IN] = 1,
> +	.b[PSC_CURRENT_IN] = 0,
> +	.R[PSC_CURRENT_IN] = 3,
> +	.m[PSC_CURRENT_OUT] = 1,
> +	.b[PSC_CURRENT_OUT] = 0,
> +	.R[PSC_CURRENT_OUT] = 2,
> +	.func[0] = 0, /* supervisor summing page without voltage readings */

As far as I can see from the manual, the actually reported values for other
attributes match those of page 1, making the values on page 0 redundant.
I think this should be mentioned in a comment to avoid confusion.


> +	.func[1] = PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT
> +	    | PMBUS_HAVE_IIN | PMBUS_HAVE_IOUT
> +	    | PMBUS_HAVE_PIN | PMBUS_HAVE_POUT
> +	    | PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_TEMP
> +	    | PMBUS_HAVE_STATUS_IOUT | PMBUS_HAVE_STATUS_INPUT,
> +	.read_word_data = pli1209bc_read_word_data,
> +};
> +
> +static int pli1209bc_probe(struct i2c_client *client)
> +{
> +	client->dev.platform_data = &pli1209bc_plat_data;
> +	return pmbus_do_probe(client, &pli1209bc_info);
> +}
> +
> +static const struct i2c_device_id pli1209bc_id[] = {
> +	{"pli1209bc", 0},
> +	{}
> +};
> +
> +MODULE_DEVICE_TABLE(i2c, pli1209bc_id);
> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id pli1209bc_of_match[] = {
> +	{ .compatible = "vicor,pli1209bc" },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, pli1209bc_of_match);
> +#endif
> +
> +/* This is the driver that will be inserted */

Pretty useless comment.

> +static struct i2c_driver pli1209bc_driver = {
> +	.driver = {
> +		   .name = "pli1209bc",
> +		   .of_match_table = of_match_ptr(pli1209bc_of_match),
> +		   },
> +	.probe_new = pli1209bc_probe,
> +	.id_table = pli1209bc_id,
> +};
> +
> +module_i2c_driver(pli1209bc_driver);
> +
> +MODULE_AUTHOR("Marcello Sylvester Bauer <sylv@sylv.io>");
> +MODULE_DESCRIPTION("PMBus driver for Vicor PLI1209BC");
> +MODULE_LICENSE("GPL");