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 */
38struct 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 */
54static 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 */
65static 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
72static 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
129static 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);
158exit:
159	mutex_unlock(&data->lock);
160	return err;
161}
162
163static 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
184static 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
190static const struct hwmon_ops sbtsi_hwmon_ops = {
191	.is_visible = sbtsi_is_visible,
192	.read = sbtsi_read,
193	.write = sbtsi_write,
194};
195
196static const struct hwmon_chip_info sbtsi_chip_info = {
197	.ops = &sbtsi_hwmon_ops,
198	.info = sbtsi_info,
199};
200
201static 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
220static const struct i2c_device_id sbtsi_id[] = {
221	{"sbtsi", 0},
222	{}
223};
224MODULE_DEVICE_TABLE(i2c, sbtsi_id);
225
226static const struct of_device_id __maybe_unused sbtsi_of_match[] = {
227	{
228		.compatible = "amd,sbtsi",
229	},
230	{ },
231};
232MODULE_DEVICE_TABLE(of, sbtsi_of_match);
233
234static 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
243module_i2c_driver(sbtsi_driver);
244
245MODULE_AUTHOR("Kun Yi <kunyi@google.com>");
246MODULE_DESCRIPTION("Hwmon driver for AMD SB-TSI emulated sensor");
247MODULE_LICENSE("GPL");
248