1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Hardware monitoring driver for Analog Devices MAX20830 4 * 5 * Copyright (C) 2026 Analog Devices, Inc. 6 */ 7 8 #include <linux/errno.h> 9 #include <linux/i2c.h> 10 #include <linux/math64.h> 11 #include <linux/module.h> 12 #include <linux/string.h> 13 #include "pmbus.h" 14 15 #define MAX20830_IC_DEVICE_ID_LENGTH 9 16 17 struct max20830_data { 18 struct pmbus_driver_info info; 19 u32 vout_rfb1; 20 u32 vout_rfb2; 21 }; 22 23 static const char * const supported_chip_ids[] = { 24 "MAX20830", 25 "MAX20830C", 26 "MAX20840C", 27 }; 28 29 /* 30 * MAX20830 only supports READ_VOUT for VOUT monitoring. 31 * 32 * Limit registers (VOUT_OV_WARN_LIMIT, VOUT_OV_FAULT_LIMIT, etc.) are not 33 * supported by this driver and return -ENODATA. This means sysfs attributes 34 * like in1_max, in1_crit, etc. will not be available. Only in1_input (the 35 * scaled output voltage) is supported. 36 * 37 * MAX20830 uses an external resistor divider for voltage sensing: 38 * - VOUT_COMMAND and VOUT_MAX set the reference voltage at the feedback pin 39 * - READ_VOUT reports the feedback voltage, which needs to be scaled for actual 40 * output voltage 41 * 42 * Scaling formula: vout_actual = vout_fb × (1 + RFB1 / RFB2) 43 * 44 * If regulator support is added in the future, some adjustments are needed to 45 * ensure correct feedback voltages are set. 46 */ 47 static int max20830_read_word_data(struct i2c_client *client, int page, 48 int phase, int reg) 49 { 50 const struct pmbus_driver_info *info = pmbus_get_driver_info(client); 51 const struct max20830_data *data = container_of(info, struct max20830_data, info); 52 int ret; 53 u64 temp; 54 55 switch (reg) { 56 case PMBUS_READ_VOUT: 57 ret = pmbus_read_word_data(client, page, phase, reg); 58 if (ret < 0) 59 return ret; 60 61 /* Apply voltage divider scaling if resistors are non-zero */ 62 if (data->vout_rfb1 && data->vout_rfb2) { 63 temp = (u64)data->vout_rfb1 + (u64)data->vout_rfb2; 64 temp = DIV_ROUND_CLOSEST_ULL((u64)ret * temp, data->vout_rfb2); 65 ret = clamp_val(temp, 0, 0xFFFF); 66 } 67 return ret; 68 default: 69 return -ENODATA; 70 } 71 } 72 73 static struct pmbus_driver_info max20830_info = { 74 .pages = 1, 75 .format[PSC_VOLTAGE_IN] = linear, 76 .format[PSC_VOLTAGE_OUT] = linear, 77 .format[PSC_CURRENT_OUT] = linear, 78 .format[PSC_TEMPERATURE] = linear, 79 .func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT | PMBUS_HAVE_IOUT | 80 PMBUS_HAVE_TEMP | 81 PMBUS_HAVE_STATUS_VOUT | PMBUS_HAVE_STATUS_IOUT | 82 PMBUS_HAVE_STATUS_INPUT | PMBUS_HAVE_STATUS_TEMP, 83 .read_word_data = max20830_read_word_data, 84 .have_pmbus_revision = true, 85 .pmbus_revision = PMBUS_REV_13, 86 }; 87 88 static int max20830_probe(struct i2c_client *client) 89 { 90 u8 buf[I2C_SMBUS_BLOCK_MAX + 1] = {}; 91 struct max20830_data *data; 92 int i, ret; 93 94 data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL); 95 if (!data) 96 return -ENOMEM; 97 98 data->info = max20830_info; 99 100 /* Read optional voltage divider resistor values */ 101 device_property_read_u32(&client->dev, "adi,vout-rfb1-ohms", &data->vout_rfb1); 102 device_property_read_u32(&client->dev, "adi,vout-rfb2-ohms", &data->vout_rfb2); 103 104 ret = pmbus_read_smbus_i2c_block_data(client, PMBUS_IC_DEVICE_ID, buf); 105 if (ret < 0) 106 return dev_err_probe(&client->dev, ret, 107 "Failed to read IC_DEVICE_ID\n"); 108 109 /* Verify we read the expected number of bytes */ 110 if (ret < MAX20830_IC_DEVICE_ID_LENGTH) 111 return dev_err_probe(&client->dev, -ENODEV, 112 "IC_DEVICE_ID too short: expected %d bytes, got %d\n", 113 MAX20830_IC_DEVICE_ID_LENGTH, ret); 114 115 /* Null-terminate the string */ 116 buf[ret] = '\0'; 117 118 /* Verify the device ID matches what we expect */ 119 for (i = 0; i < ARRAY_SIZE(supported_chip_ids); i++) { 120 if (!strcmp(buf, supported_chip_ids[i])) 121 break; 122 } 123 124 /* No match found - unsupported device */ 125 if (i == ARRAY_SIZE(supported_chip_ids)) 126 return dev_err_probe(&client->dev, -ENODEV, 127 "Unsupported device: '%*pE'\n", ret, buf); 128 129 return pmbus_do_probe(client, &data->info); 130 } 131 132 static const struct i2c_device_id max20830_id[] = { 133 {"max20830"}, 134 { } 135 }; 136 MODULE_DEVICE_TABLE(i2c, max20830_id); 137 138 static const struct of_device_id max20830_of_match[] = { 139 { .compatible = "adi,max20830" }, 140 { } 141 }; 142 MODULE_DEVICE_TABLE(of, max20830_of_match); 143 144 static struct i2c_driver max20830_driver = { 145 .driver = { 146 .name = "max20830", 147 .of_match_table = max20830_of_match, 148 }, 149 .probe = max20830_probe, 150 .id_table = max20830_id, 151 }; 152 153 module_i2c_driver(max20830_driver); 154 155 MODULE_AUTHOR("Alexis Czezar Torreno <alexisczezar.torreno@analog.com>"); 156 MODULE_DESCRIPTION("PMBus driver for Analog Devices MAX20830"); 157 MODULE_LICENSE("GPL"); 158 MODULE_IMPORT_NS("PMBUS"); 159