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1// SPDX-License-Identifier: GPL-2.02/*3 * nct6775-i2c - I2C driver for the hardware monitoring functionality of4 * Nuvoton NCT677x Super-I/O chips5 *6 * Copyright (C) 2022 Zev Weiss <zev@bewilderbeest.net>7 *8 * This driver interacts with the chip via it's "back door" i2c interface, as9 * is often exposed to a BMC. Because the host may still be operating the10 * chip via the ("front door") LPC interface, this driver cannot assume that11 * it actually has full control of the chip, and in particular must avoid12 * making any changes that could confuse the host's LPC usage of it. It thus13 * operates in a strictly read-only fashion, with the only exception being the14 * bank-select register (which seems, thankfully, to be replicated for the i2c15 * 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.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 done61 * 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 is72 * 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 { .compatible = "nuvoton,nct6799", .data = (void *)nct6799, },91 { },92};93MODULE_DEVICE_TABLE(of, nct6775_i2c_of_match);94 95static const struct i2c_device_id nct6775_i2c_id[] = {96 { "nct6106", nct6106 },97 { "nct6116", nct6116 },98 { "nct6775", nct6775 },99 { "nct6776", nct6776 },100 { "nct6779", nct6779 },101 { "nct6791", nct6791 },102 { "nct6792", nct6792 },103 { "nct6793", nct6793 },104 { "nct6795", nct6795 },105 { "nct6796", nct6796 },106 { "nct6797", nct6797 },107 { "nct6798", nct6798 },108 { "nct6799", nct6799 },109 { }110};111MODULE_DEVICE_TABLE(i2c, nct6775_i2c_id);112 113static int nct6775_i2c_probe_init(struct nct6775_data *data)114{115 u32 tsi_channel_mask;116 struct i2c_client *client = data->driver_data;117 118 /*119 * The i2c interface doesn't provide access to the control registers120 * needed to determine the presence of other fans, but fans 1 and 2121 * are (in principle) always there.122 *123 * In practice this is perhaps a little silly, because the system124 * using this driver is mostly likely a BMC, and hence probably has125 * totally separate fan tachs & pwms of its own that are actually126 * controlling/monitoring the fans -- these are thus unlikely to be127 * doing anything actually useful.128 */129 data->has_fan = 0x03;130 data->has_fan_min = 0x03;131 data->has_pwm = 0x03;132 133 /*134 * Because on a BMC this driver may be bound very shortly after power135 * is first applied to the device, the automatic TSI channel detection136 * in nct6775_probe() (which has already been run at this point) may137 * not find anything if a channel hasn't yet produced a temperature138 * reading. Augment whatever was found via autodetection (if139 * anything) with the channels DT says should be active.140 */141 if (!of_property_read_u32(client->dev.of_node, "nuvoton,tsi-channel-mask",142 &tsi_channel_mask))143 data->have_tsi_temp |= tsi_channel_mask & GENMASK(NUM_TSI_TEMP - 1, 0);144 145 return 0;146}147 148static const struct regmap_config nct6775_i2c_regmap_config = {149 .reg_bits = 16,150 .val_bits = 16,151 .reg_read = nct6775_i2c_read,152 .reg_write = nct6775_i2c_write,153};154 155static int nct6775_i2c_probe(struct i2c_client *client)156{157 struct nct6775_data *data;158 struct device *dev = &client->dev;159 160 data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);161 if (!data)162 return -ENOMEM;163 164 data->kind = (enum kinds)(uintptr_t)i2c_get_match_data(client);165 data->read_only = true;166 data->driver_data = client;167 data->driver_init = nct6775_i2c_probe_init;168 169 return nct6775_probe(dev, data, &nct6775_i2c_regmap_config);170}171 172static struct i2c_driver nct6775_i2c_driver = {173 .class = I2C_CLASS_HWMON,174 .driver = {175 .name = "nct6775-i2c",176 .of_match_table = of_match_ptr(nct6775_i2c_of_match),177 },178 .probe = nct6775_i2c_probe,179 .id_table = nct6775_i2c_id,180};181 182module_i2c_driver(nct6775_i2c_driver);183 184MODULE_AUTHOR("Zev Weiss <zev@bewilderbeest.net>");185MODULE_DESCRIPTION("I2C driver for NCT6775F and compatible chips");186MODULE_LICENSE("GPL");187MODULE_IMPORT_NS(HWMON_NCT6775);188