Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
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/of.h>
16#include <linux/bitfield.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/*
33 * Bit for reporting value with temperature measurement range.
34 * bit == 0: Use default temperature range (0C to 255.875C).
35 * bit == 1: Use extended temperature range (-49C to +206.875C).
36 */
37#define SBTSI_CONFIG_EXT_RANGE_SHIFT 2
38/*
39 * ReadOrder bit specifies the reading order of integer and decimal part of
40 * CPU temperature for atomic reads. If bit == 0, reading integer part triggers
41 * latching of the decimal part, so integer part should be read first.
42 * If bit == 1, read order should be reversed.
43 */
44#define SBTSI_CONFIG_READ_ORDER_SHIFT 5
45
46#define SBTSI_TEMP_EXT_RANGE_ADJ 49000
47
48#define SBTSI_TEMP_MIN 0
49#define SBTSI_TEMP_MAX 255875
50
51/* Each client has this additional data */
52struct sbtsi_data {
53 struct i2c_client *client;
54 bool ext_range_mode;
55 bool read_order;
56};
57
58/*
59 * From SB-TSI spec: CPU temperature readings and limit registers encode the
60 * temperature in increments of 0.125 from 0 to 255.875. The "high byte"
61 * register encodes the base-2 of the integer portion, and the upper 3 bits of
62 * the "low byte" encode in base-2 the decimal portion.
63 *
64 * e.g. INT=0x19, DEC=0x20 represents 25.125 degrees Celsius
65 *
66 * Therefore temperature in millidegree Celsius =
67 * (INT + DEC / 256) * 1000 = (INT * 8 + DEC / 32) * 125
68 */
69static inline int sbtsi_reg_to_mc(s32 integer, s32 decimal)
70{
71 return ((integer << 3) + (decimal >> 5)) * 125;
72}
73
74/*
75 * Inversely, given temperature in millidegree Celsius
76 * INT = (TEMP / 125) / 8
77 * DEC = ((TEMP / 125) % 8) * 32
78 * Caller have to make sure temp doesn't exceed 255875, the max valid value.
79 */
80static inline void sbtsi_mc_to_reg(s32 temp, u8 *integer, u8 *decimal)
81{
82 temp /= 125;
83 *integer = temp >> 3;
84 *decimal = (temp & 0x7) << 5;
85}
86
87static int sbtsi_read(struct device *dev, enum hwmon_sensor_types type,
88 u32 attr, int channel, long *val)
89{
90 struct sbtsi_data *data = dev_get_drvdata(dev);
91 s32 temp_int, temp_dec;
92
93 switch (attr) {
94 case hwmon_temp_input:
95 if (data->read_order) {
96 temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
97 temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
98 } else {
99 temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_INT);
100 temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_DEC);
101 }
102 break;
103 case hwmon_temp_max:
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 break;
107 case hwmon_temp_min:
108 temp_int = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_INT);
109 temp_dec = i2c_smbus_read_byte_data(data->client, SBTSI_REG_TEMP_LOW_DEC);
110 break;
111 default:
112 return -EINVAL;
113 }
114
115
116 if (temp_int < 0)
117 return temp_int;
118 if (temp_dec < 0)
119 return temp_dec;
120
121 *val = sbtsi_reg_to_mc(temp_int, temp_dec);
122 if (data->ext_range_mode)
123 *val -= SBTSI_TEMP_EXT_RANGE_ADJ;
124
125 return 0;
126}
127
128static int sbtsi_write(struct device *dev, enum hwmon_sensor_types type,
129 u32 attr, int channel, long val)
130{
131 struct sbtsi_data *data = dev_get_drvdata(dev);
132 int reg_int, reg_dec, err;
133 u8 temp_int, temp_dec;
134
135 switch (attr) {
136 case hwmon_temp_max:
137 reg_int = SBTSI_REG_TEMP_HIGH_INT;
138 reg_dec = SBTSI_REG_TEMP_HIGH_DEC;
139 break;
140 case hwmon_temp_min:
141 reg_int = SBTSI_REG_TEMP_LOW_INT;
142 reg_dec = SBTSI_REG_TEMP_LOW_DEC;
143 break;
144 default:
145 return -EINVAL;
146 }
147
148 if (data->ext_range_mode)
149 val += SBTSI_TEMP_EXT_RANGE_ADJ;
150 val = clamp_val(val, SBTSI_TEMP_MIN, SBTSI_TEMP_MAX);
151 sbtsi_mc_to_reg(val, &temp_int, &temp_dec);
152
153 err = i2c_smbus_write_byte_data(data->client, reg_int, temp_int);
154 if (err)
155 return err;
156
157 return i2c_smbus_write_byte_data(data->client, reg_dec, temp_dec);
158}
159
160static umode_t sbtsi_is_visible(const void *data,
161 enum hwmon_sensor_types type,
162 u32 attr, int channel)
163{
164 switch (type) {
165 case hwmon_temp:
166 switch (attr) {
167 case hwmon_temp_input:
168 return 0444;
169 case hwmon_temp_min:
170 return 0644;
171 case hwmon_temp_max:
172 return 0644;
173 }
174 break;
175 default:
176 break;
177 }
178 return 0;
179}
180
181static const struct hwmon_channel_info * const sbtsi_info[] = {
182 HWMON_CHANNEL_INFO(chip, HWMON_C_REGISTER_TZ),
183 HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT | HWMON_T_MIN | HWMON_T_MAX),
184 NULL
185};
186
187static const struct hwmon_ops sbtsi_hwmon_ops = {
188 .is_visible = sbtsi_is_visible,
189 .read = sbtsi_read,
190 .write = sbtsi_write,
191};
192
193static const struct hwmon_chip_info sbtsi_chip_info = {
194 .ops = &sbtsi_hwmon_ops,
195 .info = sbtsi_info,
196};
197
198static int sbtsi_probe(struct i2c_client *client)
199{
200 struct device *dev = &client->dev;
201 struct device *hwmon_dev;
202 struct sbtsi_data *data;
203 int err;
204
205 data = devm_kzalloc(dev, sizeof(struct sbtsi_data), GFP_KERNEL);
206 if (!data)
207 return -ENOMEM;
208
209 data->client = client;
210
211 err = i2c_smbus_read_byte_data(data->client, SBTSI_REG_CONFIG);
212 if (err < 0)
213 return err;
214 data->ext_range_mode = FIELD_GET(BIT(SBTSI_CONFIG_EXT_RANGE_SHIFT), err);
215 data->read_order = FIELD_GET(BIT(SBTSI_CONFIG_READ_ORDER_SHIFT), err);
216
217 hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, data,
218 &sbtsi_chip_info, NULL);
219
220 return PTR_ERR_OR_ZERO(hwmon_dev);
221}
222
223static const struct i2c_device_id sbtsi_id[] = {
224 {"sbtsi"},
225 {}
226};
227MODULE_DEVICE_TABLE(i2c, sbtsi_id);
228
229static const struct of_device_id __maybe_unused sbtsi_of_match[] = {
230 {
231 .compatible = "amd,sbtsi",
232 },
233 { },
234};
235MODULE_DEVICE_TABLE(of, sbtsi_of_match);
236
237static struct i2c_driver sbtsi_driver = {
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
246module_i2c_driver(sbtsi_driver);
247
248MODULE_AUTHOR("Kun Yi <kunyi@google.com>");
249MODULE_DESCRIPTION("Hwmon driver for AMD SB-TSI emulated sensor");
250MODULE_LICENSE("GPL");