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