drivers/hwmon/sbtsi_temp.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * sbtsi_temp.c - hwmon driver for a SBI Temperature Sensor Interface (SB-TSI)
   4  *                compliant AMD SoC temperature device.
   5  *
   6  * Copyright (c) 2020, Google Inc.
   7  * Copyright (c) 2020, Kun Yi <kunyi@google.com>
   8  */
   9
  10 #include <linux/err.h>
  11 #include <linux/i2c.h>
  12 #include <linux/init.h>
  13 #include <linux/hwmon.h>
  14 #include <linux/module.h>
  15 #include <linux/mutex.h>
  16 #include <linux/of_device.h>
  17 #include <linux/of.h>
  18
  19 /*
  20  * SB-TSI registers only support SMBus byte data access. "_INT" registers are
  21  * the integer part of a temperature value or limit, and "_DEC" registers are
  22  * corresponding decimal parts.
  23  */
  24 #define SBTSI_REG_TEMP_INT              0x01 /* RO */
  25 #define SBTSI_REG_STATUS                0x02 /* RO */
  26 #define SBTSI_REG_CONFIG                0x03 /* RO */
  27 #define SBTSI_REG_TEMP_HIGH_INT         0x07 /* RW */
  28 #define SBTSI_REG_TEMP_LOW_INT          0x08 /* RW */
  29 #define SBTSI_REG_TEMP_DEC              0x10 /* RW */
  30 #define SBTSI_REG_TEMP_HIGH_DEC         0x13 /* RW */
  31 #define SBTSI_REG_TEMP_LOW_DEC          0x14 /* RW */
  32
  33 #define SBTSI_CONFIG_READ_ORDER_SHIFT   5
  34
  35 #define SBTSI_TEMP_MIN  0
  36 #define SBTSI_TEMP_MAX  255875
  37
  38 /* Each client has this additional data */
  39 struct sbtsi_data {
  40         struct i2c_client *client;
  41         struct mutex lock;
  42 };
  43
  44 /*
  45  * From SB-TSI spec: CPU temperature readings and limit registers encode the
  46  * temperature in increments of 0.125 from 0 to 255.875. The "high byte"
  47  * register encodes the base-2 of the integer portion, and the upper 3 bits of
  48  * the "low byte" encode in base-2 the decimal portion.
  49  *
  50  * e.g. INT=0x19, DEC=0x20 represents 25.125 degrees Celsius
  51  *
  52  * Therefore temperature in millidegree Celsius =
  53  *   (INT + DEC / 256) * 1000 = (INT * 8 + DEC / 32) * 125
  54  */
  55 static inline int sbtsi_reg_to_mc(s32 integer, s32 decimal)
  56 {
  57         return ((integer << 3) + (decimal >> 5)) * 125;
  58 }
  59
  60 /*
  61  * Inversely, given temperature in millidegree Celsius
  62  *   INT = (TEMP / 125) / 8
  63  *   DEC = ((TEMP / 125) % 8) * 32
  64  * Caller have to make sure temp doesn't exceed 255875, the max valid value.
  65  */
  66 static inline void sbtsi_mc_to_reg(s32 temp, u8 *integer, u8 *decimal)
  67 {
  68         temp /= 125;
  69         *integer = temp >> 3;
  70         *decimal = (temp & 0x7) << 5;
  71 }
  72
  73 static int sbtsi_read(struct device *dev, enum hwmon_sensor_types type,
  74                       u32 attr, int channel, long *val)
  75 {
  76         struct sbtsi_data *data = dev_get_drvdata(dev);
  77         s32 temp_int, temp_dec;
  78         int err;
  79
  80         switch (attr) {
  81         case hwmon_temp_input:
  82                 /*
  83                  * ReadOrder bit specifies the reading order of integer and
  84                  * decimal part of CPU temp for atomic reads. If bit == 0,
  85                  * reading integer part triggers latching of the decimal part,
  86                  * so integer part should be read first. If bit == 1, read
  87                  * order should be reversed.
  88                  */
  89                 err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
  90                 if (err < 0)
  91                         return err;
  92
  93                 mutex_lock(&data->lock);
  94                 if (err & BIT(SBTSI_CONFIG_READ_ORDER_SHIFT)) {
  95                         temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
  96                         temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
  97                 } else {
  98                         temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
  99                         temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
 100                 }
 101                 mutex_unlock(&data->lock);
 102                 break;
 103         case hwmon_temp_max:
 104                 mutex_lock(&data->lock);
 105                 temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_INT);
 106                 temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_HIGH_DEC);
 107                 mutex_unlock(&data->lock);
 108                 break;
 109         case hwmon_temp_min:
 110                 mutex_lock(&data->lock);
 111                 temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_INT);
 112                 temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_DEC);
 113                 mutex_unlock(&data->lock);
 114                 break;
 115         default:
 116                 return -EINVAL;
 117         }
 118
 119
 120         if (temp_int < 0)
 121                 return temp_int;
 122         if (temp_dec < 0)
 123                 return temp_dec;
 124
 125         *val = sbtsi_reg_to_mc(temp_int, temp_dec);
 126
 127         return 0;
 128 }
 129
 130 static int sbtsi_write(struct device *dev, enum hwmon_sensor_types type,
 131                        u32 attr, int channel, long val)
 132 {
 133         struct sbtsi_data *data = dev_get_drvdata(dev);
 134         int reg_int, reg_dec, err;
 135         u8 temp_int, temp_dec;
 136
 137         switch (attr) {
 138         case hwmon_temp_max:
 139                 reg_int = SBTSI_REG_TEMP_HIGH_INT;
 140                 reg_dec = SBTSI_REG_TEMP_HIGH_DEC;
 141                 break;
 142         case hwmon_temp_min:
 143                 reg_int = SBTSI_REG_TEMP_LOW_INT;
 144                 reg_dec = SBTSI_REG_TEMP_LOW_DEC;
 145                 break;
 146         default:
 147                 return -EINVAL;
 148         }
 149
 150         val = clamp_val(val, SBTSI_TEMP_MIN, SBTSI_TEMP_MAX);
 151         sbtsi_mc_to_reg(val, &temp_int, &temp_dec);
 152
 153         mutex_lock(&data->lock);
 154         err = i2c_smbus_write_byte_data(data->client, reg_int, temp_int);
 155         if (err)
 156                 goto exit;
 157
 158         err = i2c_smbus_write_byte_data(data->client, reg_dec, temp_dec);
 159 exit:
 160         mutex_unlock(&data->lock);
 161         return err;
 162 }
 163
 164 static umode_t sbtsi_is_visible(const void *data,
 165                                 enum hwmon_sensor_types type,
 166                                 u32 attr, int channel)
 167 {
 168         switch (type) {
 169         case hwmon_temp:
 170                 switch (attr) {
 171                 case hwmon_temp_input:
 172                         return 0444;
 173                 case hwmon_temp_min:
 174                         return 0644;
 175                 case hwmon_temp_max:
 176                         return 0644;
 177                 }
 178                 break;
 179         default:
 180                 break;
 181         }
 182         return 0;
 183 }
 184
 185 static const struct hwmon_channel_info *sbtsi_info[] = {
 186         HWMON_CHANNEL_INFO(chip, HWMON_C_REGISTER_TZ),
 187         HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT | HWMON_T_MIN | HWMON_T_MAX),
 188         NULL
 189 };
 190
 191 static const struct hwmon_ops sbtsi_hwmon_ops = {
 192         .is_visible = sbtsi_is_visible,
 193         .read = sbtsi_read,
 194         .write = sbtsi_write,
 195 };
 196
 197 static const struct hwmon_chip_info sbtsi_chip_info = {
 198         .ops = &sbtsi_hwmon_ops,
 199         .info = sbtsi_info,
 200 };
 201
 202 static int sbtsi_probe(struct i2c_client *client,
 203                        const struct i2c_device_id *id)
 204 {
 205         struct device *dev = &client->dev;
 206         struct device *hwmon_dev;
 207         struct sbtsi_data *data;
 208
 209         data = devm_kzalloc(dev, sizeof(struct sbtsi_data), GFP_KERNEL);
 210         if (!data)
 211                 return -ENOMEM;
 212
 213         data->client = client;
 214         mutex_init(&data->lock);
 215
 216         hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, data, &sbtsi_chip_info,
 217                                                          NULL);
 218
 219         return PTR_ERR_OR_ZERO(hwmon_dev);
 220 }
 221
 222 static const struct i2c_device_id sbtsi_id[] = {
 223         {"sbtsi", 0},
 224         {}
 225 };
 226 MODULE_DEVICE_TABLE(i2c, sbtsi_id);
 227
 228 static const struct of_device_id __maybe_unused sbtsi_of_match[] = {
 229         {
 230                 .compatible = "amd,sbtsi",
 231         },
 232         { },
 233 };
 234 MODULE_DEVICE_TABLE(of, sbtsi_of_match);
 235
 236 static struct i2c_driver sbtsi_driver = {
 237         .class = I2C_CLASS_HWMON,
 238         .driver = {
 239                 .name = "sbtsi",
 240                 .of_match_table = of_match_ptr(sbtsi_of_match),
 241         },
 242         .probe = sbtsi_probe,
 243         .id_table = sbtsi_id,
 244 };
 245
 246 module_i2c_driver(sbtsi_driver);
 247
 248 MODULE_AUTHOR("Kun Yi <kunyi@google.com>");
 249 MODULE_DESCRIPTION("Hwmon driver for AMD SB-TSI emulated sensor");
 250 MODULE_LICENSE("GPL");