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", 0}, 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 .class = I2C_CLASS_HWMON, 236 .driver = { 237 .name = "sbtsi", 238 .of_match_table = of_match_ptr(sbtsi_of_match), 239 }, 240 .probe = sbtsi_probe, 241 .id_table = sbtsi_id, 242 }; 243 244 module_i2c_driver(sbtsi_driver); 245 246 MODULE_AUTHOR("Kun Yi <kunyi@google.com>"); 247 MODULE_DESCRIPTION("Hwmon driver for AMD SB-TSI emulated sensor"); 248 MODULE_LICENSE("GPL"); 249