drivers/hwmon/nct6775-i2c.c

   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.h>
  25 #include <linux/regmap.h>
  26 #include "nct6775.h"
  27
  28 static 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  */
  63 static 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
  77 static 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 };
  93 MODULE_DEVICE_TABLE(of, nct6775_i2c_of_match);
  94
  95 static 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 };
 111 MODULE_DEVICE_TABLE(i2c, nct6775_i2c_id);
 112
 113 static 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 registers
 120          * needed to determine the presence of other fans, but fans 1 and 2
 121          * are (in principle) always there.
 122          *
 123          * In practice this is perhaps a little silly, because the system
 124          * using this driver is mostly likely a BMC, and hence probably has
 125          * totally separate fan tachs & pwms of its own that are actually
 126          * controlling/monitoring the fans -- these are thus unlikely to be
 127          * 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 power
 135          * is first applied to the device, the automatic TSI channel detection
 136          * in nct6775_probe() (which has already been run at this point) may
 137          * not find anything if a channel hasn't yet produced a temperature
 138          * reading.  Augment whatever was found via autodetection (if
 139          * 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
 148 static 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
 155 static 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
 172 static 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
 182 module_i2c_driver(nct6775_i2c_driver);
 183
 184 MODULE_AUTHOR("Zev Weiss <zev@bewilderbeest.net>");
 185 MODULE_DESCRIPTION("I2C driver for NCT6775F and compatible chips");
 186 MODULE_LICENSE("GPL");
 187 MODULE_IMPORT_NS("HWMON_NCT6775");