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// SPDX-License-Identifier: GPL-2.0
/*
* Hardware monitoring driver for Analog Devices MAX20830
*
* Copyright (C) 2026 Analog Devices, Inc.
*/
#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;
};
static const char * const supported_chip_ids[] = {
"MAX20830",
"MAX20830C",
"MAX20840C",
};
/*
* 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,
.format[PSC_VOLTAGE_OUT] = linear,
.format[PSC_CURRENT_OUT] = linear,
.format[PSC_TEMPERATURE] = linear,
.func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT |
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,
};
static int max20830_probe(struct i2c_client *client)
{
u8 buf[I2C_SMBUS_BLOCK_MAX + 1] = {};
struct max20830_data *data;
int i, 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);
ret = pmbus_read_smbus_i2c_block_data(client, PMBUS_IC_DEVICE_ID, buf);
if (ret < 0)
return dev_err_probe(&client->dev, ret,
"Failed to read IC_DEVICE_ID\n");
/* Verify we read the expected number of bytes */
if (ret < MAX20830_IC_DEVICE_ID_LENGTH)
return dev_err_probe(&client->dev, -ENODEV,
"IC_DEVICE_ID too short: expected %d bytes, got %d\n",
MAX20830_IC_DEVICE_ID_LENGTH, ret);
/* Null-terminate the string */
buf[ret] = '\0';
/* Verify the device ID matches what we expect */
for (i = 0; i < ARRAY_SIZE(supported_chip_ids); i++) {
if (!strcmp(buf, supported_chip_ids[i]))
break;
}
/* No match found - unsupported device */
if (i == ARRAY_SIZE(supported_chip_ids))
return dev_err_probe(&client->dev, -ENODEV,
"Unsupported device: '%*pE'\n", ret, buf);
return pmbus_do_probe(client, &data->info);
}
static const struct i2c_device_id max20830_id[] = {
{"max20830"},
{ }
};
MODULE_DEVICE_TABLE(i2c, max20830_id);
static const struct of_device_id max20830_of_match[] = {
{ .compatible = "adi,max20830" },
{ }
};
MODULE_DEVICE_TABLE(of, max20830_of_match);
static struct i2c_driver max20830_driver = {
.driver = {
.name = "max20830",
.of_match_table = max20830_of_match,
},
.probe = max20830_probe,
.id_table = max20830_id,
};
module_i2c_driver(max20830_driver);
MODULE_AUTHOR("Alexis Czezar Torreno <alexisczezar.torreno@analog.com>");
MODULE_DESCRIPTION("PMBus driver for Analog Devices MAX20830");
MODULE_LICENSE("GPL");
MODULE_IMPORT_NS("PMBUS");
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