nct6775-i2c.c (6171B)
1// SPDX-License-Identifier: GPL-2.0 2/* 3 * nct6775-i2c - I2C driver for the hardware monitoring functionality of 4 * Nuvoton NCT677x Super-I/O chips 5 * 6 * Copyright (C) 2022 Zev Weiss <zev@bewilderbeest.net> 7 * 8 * This driver interacts with the chip via it's "back door" i2c interface, as 9 * is often exposed to a BMC. Because the host may still be operating the 10 * chip via the ("front door") LPC interface, this driver cannot assume that 11 * it actually has full control of the chip, and in particular must avoid 12 * making any changes that could confuse the host's LPC usage of it. It thus 13 * operates in a strictly read-only fashion, with the only exception being the 14 * bank-select register (which seems, thankfully, to be replicated for the i2c 15 * interface so it doesn't affect the LPC interface). 16 */ 17 18#include <linux/module.h> 19#include <linux/init.h> 20#include <linux/i2c.h> 21#include <linux/hwmon.h> 22#include <linux/hwmon-sysfs.h> 23#include <linux/err.h> 24#include <linux/of_device.h> 25#include <linux/regmap.h> 26#include "nct6775.h" 27 28static int nct6775_i2c_read(void *ctx, unsigned int reg, unsigned int *val) 29{ 30 int ret; 31 u32 tmp; 32 u8 bank = reg >> 8; 33 struct nct6775_data *data = ctx; 34 struct i2c_client *client = data->driver_data; 35 36 if (bank != data->bank) { 37 ret = i2c_smbus_write_byte_data(client, NCT6775_REG_BANK, bank); 38 if (ret) 39 return ret; 40 data->bank = bank; 41 } 42 43 ret = i2c_smbus_read_byte_data(client, reg & 0xff); 44 if (ret < 0) 45 return ret; 46 tmp = ret; 47 48 if (nct6775_reg_is_word_sized(data, reg)) { 49 ret = i2c_smbus_read_byte_data(client, (reg & 0xff) + 1); 50 if (ret < 0) 51 return ret; 52 tmp = (tmp << 8) | ret; 53 } 54 55 *val = tmp; 56 return 0; 57} 58 59/* 60 * The write operation is a dummy so as not to disturb anything being done 61 * with the chip via LPC. 62 */ 63static int nct6775_i2c_write(void *ctx, unsigned int reg, unsigned int value) 64{ 65 struct nct6775_data *data = ctx; 66 struct i2c_client *client = data->driver_data; 67 68 dev_dbg(&client->dev, "skipping attempted write: %02x -> %03x\n", value, reg); 69 70 /* 71 * This is a lie, but writing anything but the bank-select register is 72 * something this driver shouldn't be doing. 73 */ 74 return 0; 75} 76 77static const struct of_device_id __maybe_unused nct6775_i2c_of_match[] = { 78 { .compatible = "nuvoton,nct6106", .data = (void *)nct6106, }, 79 { .compatible = "nuvoton,nct6116", .data = (void *)nct6116, }, 80 { .compatible = "nuvoton,nct6775", .data = (void *)nct6775, }, 81 { .compatible = "nuvoton,nct6776", .data = (void *)nct6776, }, 82 { .compatible = "nuvoton,nct6779", .data = (void *)nct6779, }, 83 { .compatible = "nuvoton,nct6791", .data = (void *)nct6791, }, 84 { .compatible = "nuvoton,nct6792", .data = (void *)nct6792, }, 85 { .compatible = "nuvoton,nct6793", .data = (void *)nct6793, }, 86 { .compatible = "nuvoton,nct6795", .data = (void *)nct6795, }, 87 { .compatible = "nuvoton,nct6796", .data = (void *)nct6796, }, 88 { .compatible = "nuvoton,nct6797", .data = (void *)nct6797, }, 89 { .compatible = "nuvoton,nct6798", .data = (void *)nct6798, }, 90 { }, 91}; 92MODULE_DEVICE_TABLE(of, nct6775_i2c_of_match); 93 94static const struct i2c_device_id nct6775_i2c_id[] = { 95 { "nct6106", nct6106 }, 96 { "nct6116", nct6116 }, 97 { "nct6775", nct6775 }, 98 { "nct6776", nct6776 }, 99 { "nct6779", nct6779 }, 100 { "nct6791", nct6791 }, 101 { "nct6792", nct6792 }, 102 { "nct6793", nct6793 }, 103 { "nct6795", nct6795 }, 104 { "nct6796", nct6796 }, 105 { "nct6797", nct6797 }, 106 { "nct6798", nct6798 }, 107 { } 108}; 109MODULE_DEVICE_TABLE(i2c, nct6775_i2c_id); 110 111static int nct6775_i2c_probe_init(struct nct6775_data *data) 112{ 113 u32 tsi_channel_mask; 114 struct i2c_client *client = data->driver_data; 115 116 /* 117 * The i2c interface doesn't provide access to the control registers 118 * needed to determine the presence of other fans, but fans 1 and 2 119 * are (in principle) always there. 120 * 121 * In practice this is perhaps a little silly, because the system 122 * using this driver is mostly likely a BMC, and hence probably has 123 * totally separate fan tachs & pwms of its own that are actually 124 * controlling/monitoring the fans -- these are thus unlikely to be 125 * doing anything actually useful. 126 */ 127 data->has_fan = 0x03; 128 data->has_fan_min = 0x03; 129 data->has_pwm = 0x03; 130 131 /* 132 * Because on a BMC this driver may be bound very shortly after power 133 * is first applied to the device, the automatic TSI channel detection 134 * in nct6775_probe() (which has already been run at this point) may 135 * not find anything if a channel hasn't yet produced a temperature 136 * reading. Augment whatever was found via autodetection (if 137 * anything) with the channels DT says should be active. 138 */ 139 if (!of_property_read_u32(client->dev.of_node, "nuvoton,tsi-channel-mask", 140 &tsi_channel_mask)) 141 data->have_tsi_temp |= tsi_channel_mask & GENMASK(NUM_TSI_TEMP - 1, 0); 142 143 return 0; 144} 145 146static const struct regmap_config nct6775_i2c_regmap_config = { 147 .reg_bits = 16, 148 .val_bits = 16, 149 .reg_read = nct6775_i2c_read, 150 .reg_write = nct6775_i2c_write, 151}; 152 153static int nct6775_i2c_probe(struct i2c_client *client) 154{ 155 struct nct6775_data *data; 156 const struct of_device_id *of_id; 157 const struct i2c_device_id *i2c_id; 158 struct device *dev = &client->dev; 159 160 of_id = of_match_device(nct6775_i2c_of_match, dev); 161 i2c_id = i2c_match_id(nct6775_i2c_id, client); 162 163 if (of_id && (unsigned long)of_id->data != i2c_id->driver_data) 164 dev_notice(dev, "Device mismatch: %s in device tree, %s detected\n", 165 of_id->name, i2c_id->name); 166 167 data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL); 168 if (!data) 169 return -ENOMEM; 170 171 data->kind = i2c_id->driver_data; 172 173 data->read_only = true; 174 data->driver_data = client; 175 data->driver_init = nct6775_i2c_probe_init; 176 177 return nct6775_probe(dev, data, &nct6775_i2c_regmap_config); 178} 179 180static struct i2c_driver nct6775_i2c_driver = { 181 .class = I2C_CLASS_HWMON, 182 .driver = { 183 .name = "nct6775-i2c", 184 .of_match_table = of_match_ptr(nct6775_i2c_of_match), 185 }, 186 .probe_new = nct6775_i2c_probe, 187 .id_table = nct6775_i2c_id, 188}; 189 190module_i2c_driver(nct6775_i2c_driver); 191 192MODULE_AUTHOR("Zev Weiss <zev@bewilderbeest.net>"); 193MODULE_DESCRIPTION("I2C driver for NCT6775F and compatible chips"); 194MODULE_LICENSE("GPL"); 195MODULE_IMPORT_NS(HWMON_NCT6775);