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hwmon: (pmbus/max20830): add VOUT feedback resistor scaling support

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Implement support for external voltage divider scaling using the
adi,vout-rfb1-ohms and adi,vout-rfb2-ohms device tree properties.

When the desired output voltage exceeds VREF, a resistor divider
(RFB1 and RFB2) is used to scale down the feedback voltage. The
driver reads these resistor values from device tree and applies
the scaling formula: VOUT_actual = VOUT_measured × (1 + RFB1/RFB2)

The properties are optional. If not specified, the driver assumes
no voltage divider is present and reports the raw VOUT reading.

Signed-off-by: Alexis Czezar Torreno <alexisczezar.torreno@analog.com>
Link: https://lore.kernel.org/r/20260730-dev-max20830c-v5-2-a7553f84ee74@analog.com
[groeck: Fixed minor conflicts]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
Alexis Czezar Torreno 2026-07-30 09:03:34 +08:00 committed by Guenter Roeck
parent b8efcfca43
commit fdd78852b0
1 changed files with 64 additions and 1 deletions
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65
drivers/hwmon/pmbus/max20830.c
View File

@ -7,12 +7,63 @@
#include <linux/errno.h>
#include <linux/i2c.h>
#include <linux/math64.h>
#include <linux/module.h>
#include <linux/string.h>
#include "pmbus.h"
#define MAX20830_IC_DEVICE_ID_LENGTH 9
struct max20830_data {
struct pmbus_driver_info info;
u32 vout_rfb1;
u32 vout_rfb2;
};
/*
* MAX20830 only supports READ_VOUT for VOUT monitoring.
*
* Limit registers (VOUT_OV_WARN_LIMIT, VOUT_OV_FAULT_LIMIT, etc.) are not
* supported by this driver and return -ENODATA. This means sysfs attributes
* like in1_max, in1_crit, etc. will not be available. Only in1_input (the
* scaled output voltage) is supported.
*
* MAX20830 uses an external resistor divider for voltage sensing:
* - VOUT_COMMAND and VOUT_MAX set the reference voltage at the feedback pin
* - READ_VOUT reports the feedback voltage, which needs to be scaled for actual
* output voltage
*
* Scaling formula: vout_actual = vout_fb × (1 + RFB1 / RFB2)
*
* If regulator support is added in the future, some adjustments are needed to
* ensure correct feedback voltages are set.
*/
static int max20830_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 max20830_data *data = container_of(info, struct max20830_data, info);
int ret;
u64 temp;
switch (reg) {
case PMBUS_READ_VOUT:
ret = pmbus_read_word_data(client, page, phase, reg);
if (ret < 0)
return ret;
/* Apply voltage divider scaling if resistors are non-zero */
if (data->vout_rfb1 && data->vout_rfb2) {
temp = (u64)data->vout_rfb1 + (u64)data->vout_rfb2;
temp = DIV_ROUND_CLOSEST_ULL((u64)ret * temp, data->vout_rfb2);
ret = clamp_val(temp, 0, 0xFFFF);
}
return ret;
default:
return -ENODATA;
}
}
static struct pmbus_driver_info max20830_info = {
.pages = 1,
.format[PSC_VOLTAGE_IN] = linear,
@ -23,6 +74,7 @@ static struct pmbus_driver_info max20830_info = {
PMBUS_HAVE_TEMP |
PMBUS_HAVE_STATUS_VOUT | PMBUS_HAVE_STATUS_IOUT |
PMBUS_HAVE_STATUS_INPUT | PMBUS_HAVE_STATUS_TEMP,
.read_word_data = max20830_read_word_data,
.have_pmbus_revision = true,
.pmbus_revision = PMBUS_REV_13,
};
@ -30,8 +82,19 @@ static struct pmbus_driver_info max20830_info = {
static int max20830_probe(struct i2c_client *client)
{
u8 buf[I2C_SMBUS_BLOCK_MAX + 1] = {};
struct max20830_data *data;
int ret;
data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
if (!data)
return -ENOMEM;
data->info = max20830_info;
/* Read optional voltage divider resistor values */
device_property_read_u32(&client->dev, "adi,vout-rfb1-ohms", &data->vout_rfb1);
device_property_read_u32(&client->dev, "adi,vout-rfb2-ohms", &data->vout_rfb2);
if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_BLOCK_DATA) &&
!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK))
return -ENODEV;
@ -79,7 +142,7 @@ static int max20830_probe(struct i2c_client *client)
return dev_err_probe(&client->dev, -ENODEV,
"Unsupported device: '%s'\n", buf);
return pmbus_do_probe(client, &max20830_info);
return pmbus_do_probe(client, &data->info);
}
static const struct i2c_device_id max20830_id[] = {