Re: [PATCH 2/2] hwmon: pmbus: adp1050 : Add driver support

[Guenter Roeck <linux@roeck-us.net>]

On 3/18/24 04:21, Radu Sabau wrote:
> Add support for ADP1050 Digital Controller for Isolated Power Supplies
> with PMBus interface Voltage, Current and Temperature Monitor.
> 
> The ADP1050 implements several features to enable a robust
> system of parallel and redundant operation for customers who
> require high availability. The device can measure voltage,
> current and temperature that can be used in different
> techniques to identify and safely shut down an erroneous
> power supply in parallel operation mode.
> 
> Signed-off-by: Radu Sabau <radu.sabau@analog.com>
> ---
>   Documentation/hwmon/adp1050.rst |  69 ++++++++++++++++++++
>   Documentation/hwmon/index.rst   |   1 +
>   drivers/hwmon/pmbus/Kconfig     |  10 +++
>   drivers/hwmon/pmbus/Makefile    |   1 +
>   drivers/hwmon/pmbus/adp1050.c   | 111 ++++++++++++++++++++++++++++++++
>   5 files changed, 192 insertions(+)
>   create mode 100644 Documentation/hwmon/adp1050.rst
>   create mode 100644 drivers/hwmon/pmbus/adp1050.c
> 
> diff --git a/Documentation/hwmon/adp1050.rst b/Documentation/hwmon/adp1050.rst
> new file mode 100644
> index 000000000000..e3e5bb650a51
> --- /dev/null
> +++ b/Documentation/hwmon/adp1050.rst
> @@ -0,0 +1,69 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +Kernel driver adp1050
> +=====================
> +
> +Supported chips:
> +
> +  * Analog Devices ADP1050
> +
> +    Prefix: 'adp1050'
> +
> +    Addresses scanned: I2C 0x70 - 0x77
> +
> +    Datasheet: https://www.analog.com/media/en/technical-documentation/data-
> +sheets/ADP1050.pdf
> +
> +Authors:
> +
> +  - Radu Sabau <radu.sabau@analog.com>
> +
> +
> +Description
> +-----------
> +
> +This driver supprts hardware monitoring for Analog Devices ADP1050 Digital
> +Controller for Isolated Power Supply with PMBus interface.
> +
> +The ADP1050 is an advanced digital controller with a PMBus™
> +interface targeting high density, high efficiency dc-to-dc power
> +conversion used to monitor system temperatures, voltages and currents.
> +Through the PMBus interface, the device can monitor input/output voltages,
> +input current and temperature.
> +
> +Usage Notes
> +-----------
> +
> +This driver does not auto-detect devices. You will have to instantiate
> +the devices explicitly.
> +Please see Documentation/i2c/instantiating-devices.rst for details.
> +
> +The vin scale monitor value and iin scale monitor value can be
> +configured by a device tree property;see
> +Documentation/devicetree/bindings/hwmon/pmbus/adi,adp1050.yaml for details
> +
> +Platform data support
> +---------------------
> +
> +The driver supports standard PMBus driver platform data.
> +
> +Sysfs Attributes
> +----------------
> +
> +================= ========================================
> +in1_label         "vin"
> +in1_input         Measured input voltage
> +in1_alarm	  Input voltage alarm
> +in2_label	  "vout1"
> +in2_input	  Measured output voltage
> +in2_crit	  Critical maximum output voltage
> +in2_crit_alarm    Output voltage high alarm
> +in2_lcrit	  Critical minimum output voltage
> +in2_lcrit_alarm	  Output voltage critical low alarm
> +curr1_label	  "iin"
> +curr1_input	  Measured input current.
> +curr1_alarm	  Input current alarm
> +temp1_input       Measured temperature
> +temp1_crit	  Critical high temperature
> +temp1_crit_alarm  Chip temperature critical high alarm
> +================= ========================================
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index 1ca7a4fe1f8f..9a4fd576e6f6 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -33,6 +33,7 @@ Hardware Monitoring Kernel Drivers
>      adm1266
>      adm1275
>      adm9240
> +   adp1050
>      ads7828
>      adt7410
>      adt7411
> diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
> index 557ae0c414b0..38e794d83cc3 100644
> --- a/drivers/hwmon/pmbus/Kconfig
> +++ b/drivers/hwmon/pmbus/Kconfig
> @@ -57,6 +57,16 @@ config SENSORS_ADM1275
>   	  This driver can also be built as a module. If so, the module will
>   	  be called adm1275.
>   
> +config SENSORS_ADP1050
> +	tristate "Analog Devices ADP1050 digital controller for Power Supplies"
> +	help
> +	  If you say yes here you get hardware monitoring support for Analog
> +	  Devices ADP1050 digital controller for isolated power supply with
> +	  PMBus interface.
> +
> +	  This driver can also be built as a module. If so, the module will
> +	  be called adp1050.
> +
>   config SENSORS_BEL_PFE
>   	tristate "Bel PFE Compatible Power Supplies"
>   	help
> diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
> index f14ecf03ad77..95a8dea5e5ed 100644
> --- a/drivers/hwmon/pmbus/Makefile
> +++ b/drivers/hwmon/pmbus/Makefile
> @@ -8,6 +8,7 @@ obj-$(CONFIG_SENSORS_PMBUS)	+= pmbus.o
>   obj-$(CONFIG_SENSORS_ACBEL_FSG032) += acbel-fsg032.o
>   obj-$(CONFIG_SENSORS_ADM1266)	+= adm1266.o
>   obj-$(CONFIG_SENSORS_ADM1275)	+= adm1275.o
> +obj-$(CONFIG_SENSORS_ADP1050)	+= adp1050.o
>   obj-$(CONFIG_SENSORS_BEL_PFE)	+= bel-pfe.o
>   obj-$(CONFIG_SENSORS_BPA_RS600)	+= bpa-rs600.o
>   obj-$(CONFIG_SENSORS_DELTA_AHE50DC_FAN) += delta-ahe50dc-fan.o
> diff --git a/drivers/hwmon/pmbus/adp1050.c b/drivers/hwmon/pmbus/adp1050.c
> new file mode 100644
> index 000000000000..53198d858156
> --- /dev/null
> +++ b/drivers/hwmon/pmbus/adp1050.c
> @@ -0,0 +1,111 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Hardware monitoring driver for Analog Devices ADP1050
> + *
> + * Copyright (C) 2024 Analog Devices, Inc.
> + */
> +#include <linux/bits.h>
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include "pmbus.h"
> +
> +#define ADP1050_CHIP_PASSWORD		0xD7
> +
> +#define ADP1050_VIN_SCALE_MONITOR	0xD8
> +#define ADP1050_IIN_SCALE_MONITOR	0xD9
> +
> +static struct pmbus_driver_info adp1050_info = {
> +	.pages = 1,
> +	.format[PSC_VOLTAGE_IN] = linear,
> +	.format[PSC_VOLTAGE_OUT] = linear,
> +	.format[PSC_CURRENT_IN] = linear,
> +	.format[PSC_TEMPERATURE] = linear,
> +	.func[0] = PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT
> +		| PMBUS_HAVE_VIN | PMBUS_HAVE_STATUS_INPUT
> +		| PMBUS_HAVE_IIN | PMBUS_HAVE_TEMP
> +		| PMBUS_HAVE_STATUS_TEMP,
> +};
> +
> +static int adp1050_probe(struct i2c_client *client)
> +{
> +	u32 vin_scale_monitor, iin_scale_monitor;
> +	int ret;
> +
> +	if (!i2c_check_functionality(client->adapter,
> +				     I2C_FUNC_SMBUS_WRITE_WORD_DATA))
> +		return -ENODEV;
> +
> +	/* Unlock CHIP's password in order to be able to read/write to it's
> +	 * VIN_SCALE and IIN_SCALE registers.
> +	*/
> +	ret = i2c_smbus_write_word_data(client, ADP1050_CHIP_PASSWORD, 0xFFFF);
> +	if (ret < 0) {
> +		dev_err_probe(&client->dev, "Device can't be unlocked.\n");
> +		return ret;
> +	}
> +

> +	ret = i2c_smbus_write_word_data(client, ADP1050_CHIP_PASSWORD, 0xFFFF);
> +	if (ret < 0) {
> +		dev_err_probe(&client->dev, "Device couldn't be unlocked.\n");
> +		return ret;
> +	}
> +

The datasheet says that the factory default password is 0xffff. What if it isn't ?
Refusing to instantiate the chip because it can't be unlocked seems a bit extreme.
After all, the password _can_ be changed.

> +	/* If adi,vin-scale-monitor isn't set or is set to 0 means that the
> +	 * VIN monitor isn't used, therefore 0 is used as scale in order
> +	 * for the readings to return 0.
> +	*/
> +	if (device_property_read_u32(&client->dev, "adi,vin-scale-monitor",
> +				     &vin_scale_monitor))
> +		vin_scale_monitor = 0;
> +
> +	/* If adi,iin-scale-monitor isn't set or is set to 0 means that the
> +	 * IIN monitor isn't used, therefore 0 is used as scale in order
> +	 * for the readings to return 0.
> +	*/
> +	if (device_property_read_u32(&client->dev, "adi,iin-scale-monitor",
> +				     &iin_scale_monitor))
> +		iin_scale_monitor = 0;
> +

I don't think the "-monitor" extensions in those property names
add any value.

> +	ret = i2c_smbus_write_word_data(client, ADP1050_VIN_SCALE_MONITOR,
> +					vin_scale_monitor);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = i2c_smbus_write_word_data(client, ADP1050_IIN_SCALE_MONITOR,
> +					iin_scale_monitor);
> +	if (ret < 0)
> +		return ret;
> +

If vin and iin monitoring is disabled on purpose, why still set
PMBUS_HAVE_VIN and PMBUS_HAVE_IIN above ? Reporting input values as 0
if the values are explicitly not monitored does not make sense to me.

I am puzzled about this to start with. Unless I am missing something,
the data sheet has no indication that VIN monitoring and/or IIN monitoring
is actually turned off if iin_scale/vin_scale are set to 0. Why support
the option to disable them ? That doesn't make sense to me. Please explain
how/when this makes sense. Please also explain why chip support is made
to depend on devicetree support. Register values may have been be set by
rommon/bios or (much more likely) by manufacturing, or users could just
want to keep the chip default. Why force-override it or even force-disable
it ?

Thanks,
Guenter