Message-ID: <03da3b10-dfe9-466a-9dc9-b51e29938e3e@roeck-us.net>
Date: Mon, 12 Jan 2026 13:51:34 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: ASHISH YADAV <ashishyadav78@...il.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Cc: linux-hwmon@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, ASHISH YADAV <Ashish.Yadav@...ineon.com>
Subject: Re: [PATCH v2 1/2] hwmon:(pmbus/tda38740a) TDA38740A Voltage
 Regulator Driver

On 1/7/26 06:45, ASHISH YADAV wrote:
> Add the pmbus driver for the Infineon TDA38740A/TDA38725A
> DC-DC voltage regulator.
> 
> Signed-off-by: ASHISH YADAV <Ashish.Yadav@...ineon.com>
> ---
> Changes in v2:
>   - Review comments address.

That is not a change log.

>   - Another Patch for Devicetree binding submitted for Driver
>     Documentation.
> ---
>   drivers/hwmon/pmbus/Kconfig     |  16 +++
>   drivers/hwmon/pmbus/Makefile    |   1 +
>   drivers/hwmon/pmbus/tda38740a.c | 203 ++++++++++++++++++++++++++++++++

Documentation is missing.

>   3 files changed, 220 insertions(+)
>   create mode 100644 drivers/hwmon/pmbus/tda38740a.c
> 
> diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
> index f3fb94cebf1a..e7d7ff1b57df 100644
> --- a/drivers/hwmon/pmbus/Kconfig
> +++ b/drivers/hwmon/pmbus/Kconfig
> @@ -602,6 +602,22 @@ config SENSORS_TDA38640_REGULATOR
>   	  If you say yes here you get regulator support for Infineon
>   	  TDA38640 as regulator.
>   
> +config SENSORS_TDA38740A
> +	tristate "Infineon TDA38740A"
> +	help
> +	  If you say yes here you get hardware monitoring support for Infineon
> +	  TDA38740A/25A.
> +
> +	  This driver can also be built as a module. If so, the module will
> +	  be called tda38740a.
> +
> +config SENSORS_TDA38740A_REGULATOR
> +	bool "Regulator support for TDA38740A and compatibles"
> +	depends on SENSORS_TDA38740A && REGULATOR
> +	help
> +	  If you say yes here you get regulator support for Infineon
> +	  TDA38740A/25A as regulator.
> +
>   config SENSORS_TPS25990
>   	tristate "TI TPS25990"
>   	help
> diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
> index 349a89b6d92e..f422c80cf3d8 100644
> --- a/drivers/hwmon/pmbus/Makefile
> +++ b/drivers/hwmon/pmbus/Makefile
> @@ -58,6 +58,7 @@ obj-$(CONFIG_SENSORS_PXE1610)	+= pxe1610.o
>   obj-$(CONFIG_SENSORS_Q54SJ108A2)	+= q54sj108a2.o
>   obj-$(CONFIG_SENSORS_STPDDC60)	+= stpddc60.o
>   obj-$(CONFIG_SENSORS_TDA38640)	+= tda38640.o
> +obj-$(CONFIG_SENSORS_TDA38740A)  += tda38740a.o
>   obj-$(CONFIG_SENSORS_TPS25990)	+= tps25990.o
>   obj-$(CONFIG_SENSORS_TPS40422)	+= tps40422.o
>   obj-$(CONFIG_SENSORS_TPS53679)	+= tps53679.o
> diff --git a/drivers/hwmon/pmbus/tda38740a.c b/drivers/hwmon/pmbus/tda38740a.c
> new file mode 100644
> index 000000000000..b31e1b5c6916
> --- /dev/null
> +++ b/drivers/hwmon/pmbus/tda38740a.c
> @@ -0,0 +1,203 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/**
> + * Hardware monitoring driver for Infineon Integrated-pol-voltage-regulators
> + * Driver for TDA38725A and TDA38740A
> + *
> + * Copyright (c) 2025 Infineon Technologies
> + */
> +
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/regulator/driver.h>
> +#include "pmbus.h"
> +
> +#define TDA38725A_IC_DEVICE_ID "\xA9"
> +#define TDA38740A_IC_DEVICE_ID "\xA8"
> +
> +static const struct i2c_device_id tda38740a_id[];
> +
> +enum chips { tda38725a, tda38740a };
> +
> +struct tda38740a_data {
> +	enum chips id;
> +	struct pmbus_driver_info info;
> +	u32 vout_voltage_multiplier[2];
> +};
> +
> +#define to_tda38740a_data(x) container_of(x, struct tda38740a_data, info)
> +
> +static const struct regulator_desc __maybe_unused tda38740a_reg_desc[] = {
> +	PMBUS_REGULATOR("vout", 0),
> +};
> +
> +static int tda38740a_read_word_data(struct i2c_client *client, int page,
> +				    int phase, int reg)
> +{
> +	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
> +	const struct tda38740a_data *data = to_tda38740a_data(info);
> +	int ret;
> +
> +	/* Virtual PMBUS Command not supported */
> +	if (reg >= PMBUS_VIRT_BASE)
> +		return -ENXIO;
> +

Why is this needed (instead of just returning -ENODATA) ?

> +	switch (reg) {
> +	case PMBUS_READ_VOUT:
> +		ret = pmbus_read_word_data(client, page, phase, reg);
> +		if (ret < 0)
> +			return ret;
> +		ret = ((ret * data->vout_voltage_multiplier[0]) /
> +		       data->vout_voltage_multiplier[1]);

The need for this, especially why it would only be needed for PMBUS_READ_VOUT
but not for any other VOUT related commands, is still insufficiently explained
(and I failed to understand the rationale provided earlier).

> +		break;
> +	case PMBUS_VOUT_COMMAND:
> +	case PMBUS_VOUT_MAX:
> +	case PMBUS_VOUT_MARGIN_HIGH:
> +	case PMBUS_VOUT_MARGIN_LOW:
> +	case PMBUS_VOUT_TRANSITION_RATE:
> +	case PMBUS_VOUT_DROOP:
> +	case PMBUS_VOUT_SCALE_LOOP:
> +	case PMBUS_VOUT_OV_FAULT_LIMIT:
> +	case PMBUS_VOUT_UV_FAULT_LIMIT:
> +	case PMBUS_IOUT_OC_FAULT_LIMIT:
> +	case PMBUS_OT_FAULT_LIMIT:
> +	case PMBUS_OT_WARN_LIMIT:
> +	case PMBUS_VIN_OV_FAULT_LIMIT:
> +	case PMBUS_STATUS_WORD:
> +	case PMBUS_READ_VIN:
> +	case PMBUS_READ_IIN:
> +	case PMBUS_READ_IOUT:
> +	case PMBUS_READ_TEMPERATURE_1:
> +	case PMBUS_READ_POUT:
> +	case PMBUS_READ_PIN:
> +		ret = pmbus_read_word_data(client, page, phase, reg);

I fail to see why this would be necessary. Just return -ENODATA.

> +		break;
> +	default:
> +		ret = -ENODATA;
> +		break;
> +	}
> +	return ret;
> +}
> +
> +static struct pmbus_driver_info tda38740a_info[] = {
> +	[tda38740a] = {
> +		.pages = 1,
> +		.read_word_data = tda38740a_read_word_data,
> +		.format[PSC_VOLTAGE_IN] = linear,
> +		.format[PSC_VOLTAGE_OUT] = linear,
> +		.format[PSC_CURRENT_OUT] = linear,
> +		.format[PSC_CURRENT_IN] = linear,
> +		.format[PSC_POWER] = linear,
> +		.format[PSC_TEMPERATURE] = linear,
> +
> +		.func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_STATUS_INPUT
> +			| PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_TEMP
> +			| PMBUS_HAVE_IIN
> +			| PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT
> +			| PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT
> +			| PMBUS_HAVE_POUT | PMBUS_HAVE_PIN,
> +#if IS_ENABLED(CONFIG_SENSORS_TDA38740A_REGULATOR)
> +		.num_regulators = 1,
> +		.reg_desc = tda38740a_reg_desc,
> +#endif
> +	},
> +};
> +
> +static int tda38740a_get_device_id(struct i2c_client *client)
> +{
> +	u8 device_id[I2C_SMBUS_BLOCK_MAX + 1];
> +	enum chips id;
> +	int status;
> +
> +	status = i2c_smbus_read_block_data(client, PMBUS_IC_DEVICE_ID,
> +					   device_id);
> +	if (status < 0 || status > 1) {
> +		dev_err(&client->dev,
> +			"Failed to read Device ID or unexpected/unsupported Device\n");

How about printing the device ID here if it is unsupported ?
It could be printed as hex string.

> +		return -ENODEV;
> +	}
> +
> +	if (!memcmp(TDA38725A_IC_DEVICE_ID, device_id, 1)) {
> +		id = tda38725a;
> +	} else if (!memcmp(TDA38740A_IC_DEVICE_ID, device_id, 1)) {
> +		id = tda38740a;
> +	} else {
> +		dev_err(&client->dev, "Unsupported device with ID:%s\n",
> +			device_id);

device_id is not terminated, and it is not a user readable string.
It should be printed as hex string, or as hex byte (0xXX).

> +		return -ENODEV;
> +	}
> +
> +	return id;
> +}
> +
> +static int tda38740a_probe(struct i2c_client *client)
> +{
> +	struct device *dev = &client->dev;
> +	struct tda38740a_data *data;
> +	int chip_id;
> +
> +	if (!i2c_check_functionality(client->adapter,
> +				     I2C_FUNC_SMBUS_BYTE |
> +					     I2C_FUNC_SMBUS_BYTE_DATA |
> +					     I2C_FUNC_SMBUS_WORD_DATA |
> +					     I2C_FUNC_SMBUS_BLOCK_DATA))
> +		return -ENODEV;
> +
> +	chip_id = tda38740a_get_device_id(client);
> +	if (chip_id < 0)
> +		return chip_id;
> +
> +	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +	data->id = chip_id;
> +	memcpy(&data->info, &tda38740a_info[chip_id], sizeof(data->info));
> +
> +	if (!of_property_read_u32_array(client->dev.of_node, "infineon,vout-voltage-multiplier",
> +					data->vout_voltage_multiplier,
> +		    ARRAY_SIZE(data->vout_voltage_multiplier))) {
> +		dev_info(&client->dev,
> +			 "vout-voltage-multiplier from Device Tree:%d %d\n",
> +			 data->vout_voltage_multiplier[0],
> +			 data->vout_voltage_multiplier[1]);
> +	} else {
> +		dev_info(&client->dev,
> +			 "vout-voltage-multiplier not available from Device Tree,using default values");
> +		data->vout_voltage_multiplier[0] = 0x01;
> +		data->vout_voltage_multiplier[1] = 0x01;
> +	}
> +
> +	return pmbus_do_probe(client, &data->info);
> +}
> +
> +static const struct i2c_device_id tda38740a_id[] = { { "tda38725a", tda38725a },
> +						     { "tda38740a", tda38740a },
> +						     {} };
> +
> +MODULE_DEVICE_TABLE(i2c, tda38740a_id);
> +
> +static const struct of_device_id __maybe_unused tda38740a_of_match[] = {
> +	{ .compatible = "infineon,tda38725a", .data = (void *)tda38725a },
> +	{ .compatible = "infineon,tda38740a", .data = (void *)tda38740a },
> +	{}
> +};
> +
> +MODULE_DEVICE_TABLE(of, tda38740a_of_match);
> +
> +static struct i2c_driver tda38740a_driver = {
> +	.driver = {
> +		.name = "tda38740a",
> +		.of_match_table = of_match_ptr(tda38740a_of_match),
> +	},
> +	.probe = tda38740a_probe,
> +	.id_table = tda38740a_id,
> +};
> +
> +module_i2c_driver(tda38740a_driver);
> +
> +MODULE_AUTHOR("Ashish Yadav <Ashish.Yadav@...ineon.com>");
> +MODULE_DESCRIPTION("PMBus driver for Infineon TDA38725A/40A IPOL");
> +MODULE_LICENSE("GPL");
> +MODULE_IMPORT_NS("PMBUS");

Powered by blists - more mailing lists