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Subject: Re: [PATCH v2] hwmon: (pmbus/ir38064): Add driver for Infineon
 IR38064 Voltage Regulator
To:     Patrick Venture <venture@google.com>, jdelvare@suse.com,
        corbet@lwn.net
Cc:     Maxim Sloyko <maxims@google.com>, linux-hwmon@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20190412194348.225570-1-venture@google.com>
From:   Guenter Roeck <linux@roeck-us.net>
Message-ID: <57e7d1e5-b980-fc80-ae2f-8a0ab12a0dbd@roeck-us.net>
Date:   Fri, 12 Apr 2019 13:28:49 -0700
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On 4/12/19 12:43 PM, Patrick Venture wrote:
> From: Maxim Sloyko <maxims@google.com>
> 
> Add the pmbus driver for the Infineon ir38064 voltage regulator.
> 
> Signed-off-by: Maxim Sloyko <maxims@google.com>
> Signed-off-by: Patrick Venture <venture@google.com>
> ---
> v2:
>   - Cleaned up weird tabbing behavior in doc.
> v1:
>   - Initial patchset.
> ---
>   Documentation/hwmon/ir38064   | 64 +++++++++++++++++++++++++++++++++++
>   drivers/hwmon/pmbus/Kconfig   |  9 +++++
>   drivers/hwmon/pmbus/Makefile  |  1 +
>   drivers/hwmon/pmbus/ir38064.c | 60 ++++++++++++++++++++++++++++++++
>   4 files changed, 134 insertions(+)
>   create mode 100644 Documentation/hwmon/ir38064
>   create mode 100644 drivers/hwmon/pmbus/ir38064.c
> 
> diff --git a/Documentation/hwmon/ir38064 b/Documentation/hwmon/ir38064
> new file mode 100644
> index 0000000000000..618779a329da0
> --- /dev/null
> +++ b/Documentation/hwmon/ir38064
> @@ -0,0 +1,64 @@
> +Kernel driver ir38064
> +=====================
> +
> +Supported chips:
> +  * Infineon IR38064
> +    Prefix: 'ir38064'
> +    Addresses scanned: -
> +    Datasheet: Publicly available at the Infineon webiste
> +      https://www.infineon.com/dgdl/Infineon-IR38064MTRPBF-DS-v03_07-EN.pdf?fileId=5546d462584d1d4a0158db0d9efb67ca
> +
> +Datasheet is not publicly available.
> +
> +
> +Authors:
> +        Maxim Sloyko <maxims@google.com>
> +        Patrick Venture <venture@google.com>
> +
> +Description
> +-----------
> +
> +IR38064 is a Single-input Voltage, Synchronous Buck Regulator, DC-DC Converter.
> +
> +Usage Notes
> +-----------
> +
> +This driver does not probe for PMBus devices. You will have to instantiate
> +devices explicitly.
> +
> +Sysfs attributes
> +----------------
> +
> +curr1_label		"iout1"
> +curr1_input		Measured output current
> +curr1_crit		Critical maximum current
> +curr1_crit_alarm	Current critical high alarm
> +curr1_max		Maximum current
> +curr1_max_alarm	Current high alarm
> +
> +in1_label		"vin"
> +in1_input		Measured input voltage
> +in1_crit		Critical maximum input voltage
> +in1_crit_alarm		Input voltage critical high alarm
> +in1_min		Minimum input voltage
> +in1_min_alarm		Input voltage low alarm
> +
> +in2_label		"vout1"
> +in2_input		Measured output voltage
> +in2_lcrit		Critical minimum output voltage
> +in2_lcrit_alarm	Output voltage critical low alarm
> +in2_crit		Critical maximum output voltage
> +in2_crit_alarm		Output voltage critical high alarm
> +in2_max		Maximum output voltage
> +in2_max_alarm		Output voltage high alarm
> +in2_min		Minimum output voltage
> +in2_min_alarm		Output voltage low alarm
> +
> +power1_label		"pout1"
> +power1_input		Measured output power
> +
> +temp1_input		Measured temperature
> +temp1_crit		Critical high temperature
> +temp1_crit_alarm	Chip temperature critical high alarm
> +temp1_max		Maximum temperature
> +temp1_max_alarm	Chip temperature high alarm
> diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
> index 629cb45f8557a..de87abab990e5 100644
> --- a/drivers/hwmon/pmbus/Kconfig
> +++ b/drivers/hwmon/pmbus/Kconfig
> @@ -54,6 +54,15 @@ config SENSORS_IR35221
>   	  This driver can also be built as a module. If so, the module will
>   	  be called ir35521.
>   
> +config SENSORS_IR38064
> +	tristate "Infineon IR38064"
> +	help
> +	  If you say yes here you get hardware monitoring support for Infineon
> +	  IR38064.
> +
> +	  This driver can also be built as a module. If so, the module will
> +	  be called ir38064.
> +
>   config SENSORS_LM25066
>   	tristate "National Semiconductor LM25066 and compatibles"
>   	help
> diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
> index ea0e39518c216..7d1fa6b3c8c93 100644
> --- a/drivers/hwmon/pmbus/Makefile
> +++ b/drivers/hwmon/pmbus/Makefile
> @@ -8,6 +8,7 @@ obj-$(CONFIG_SENSORS_PMBUS)	+= pmbus.o
>   obj-$(CONFIG_SENSORS_ADM1275)	+= adm1275.o
>   obj-$(CONFIG_SENSORS_IBM_CFFPS)	+= ibm-cffps.o
>   obj-$(CONFIG_SENSORS_IR35221)	+= ir35221.o
> +obj-$(CONFIG_SENSORS_IR38064)	+= ir38064.o
>   obj-$(CONFIG_SENSORS_LM25066)	+= lm25066.o
>   obj-$(CONFIG_SENSORS_LTC2978)	+= ltc2978.o
>   obj-$(CONFIG_SENSORS_LTC3815)	+= ltc3815.o
> diff --git a/drivers/hwmon/pmbus/ir38064.c b/drivers/hwmon/pmbus/ir38064.c
> new file mode 100644
> index 0000000000000..4b957ebb6fa71
> --- /dev/null
> +++ b/drivers/hwmon/pmbus/ir38064.c
> @@ -0,0 +1,60 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Hardware monitoring driver for Infineon IR38064
> + *
> + * Copyright (c) 2017 Google Inc
> + *
> + */
> +
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include "pmbus.h"
> +
> +static struct pmbus_driver_info ir38064_info = {
> +	.pages = 1,
> +	.format[PSC_VOLTAGE_IN] = linear,
> +	.format[PSC_VOLTAGE_OUT] = direct,

The datasheet says this is linear16 format with exponent=-8.
Oddly enough, the datasheet also suggests that VOUT_MODE is
not supported, which would normally report the exponent.
I think it would be is better to implement a local read function
and fake VOUT_MODE instead of declaring direct mode, but then
I understand that it would make the code more complex. I'll
leave it up to you, but if you want to keep it as-is,
please explain in a comment that you are faking linear16
mode with exponent -8.

> +	.format[PSC_CURRENT_OUT] = linear,
> +	.format[PSC_POWER] = linear,
> +	.format[PSC_TEMPERATURE] = linear,
> +	.m[PSC_VOLTAGE_OUT] = 256,
> +	.b[PSC_VOLTAGE_OUT] = 0,
> +	.R[PSC_VOLTAGE_OUT] = 0,
> +	.func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_STATUS_INPUT
> +	    | PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_TEMP
> +	    | PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT
> +	    | PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT
> +	    | PMBUS_HAVE_POUT,
> +};
> +

Not mandatory, but the chip does support VOUT_PEAK, IOUT_PEAK,
and TEMPERATURE_PEAK, just in case you are interested adding
support for it.

Thanks,
Guenter

> +static int ir38064_probe(struct i2c_client *client,
> +			 const struct i2c_device_id *id)
> +{
> +	return pmbus_do_probe(client, id, &ir38064_info);
> +}
> +
> +static const struct i2c_device_id ir38064_id[] = {
> +	{"ir38064", 0},
> +	{}
> +};
> +
> +MODULE_DEVICE_TABLE(i2c, ir38064_id);
> +
> +/* This is the driver that will be inserted */
> +static struct i2c_driver ir38064_driver = {
> +	.driver = {
> +		   .name = "ir38064",
> +		   },
> +	.probe = ir38064_probe,
> +	.remove = pmbus_do_remove,
> +	.id_table = ir38064_id,
> +};
> +
> +module_i2c_driver(ir38064_driver);
> +
> +MODULE_AUTHOR("Maxim Sloyko <maxims@google.com>");
> +MODULE_DESCRIPTION("PMBus driver for Infineon IR38064");
> +MODULE_LICENSE("GPL");
>