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 */
 39struct 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 */
 55static 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 */
 66static 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
 73static 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
130static 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);
159exit:
160	mutex_unlock(&data->lock);
161	return err;
162}
163
164static 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
185static 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
191static const struct hwmon_ops sbtsi_hwmon_ops = {
192	.is_visible = sbtsi_is_visible,
193	.read = sbtsi_read,
194	.write = sbtsi_write,
195};
196
197static const struct hwmon_chip_info sbtsi_chip_info = {
198	.ops = &sbtsi_hwmon_ops,
199	.info = sbtsi_info,
200};
201
202static 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
222static const struct i2c_device_id sbtsi_id[] = {
223	{"sbtsi", 0},
224	{}
225};
226MODULE_DEVICE_TABLE(i2c, sbtsi_id);
227
228static const struct of_device_id __maybe_unused sbtsi_of_match[] = {
229	{
230		.compatible = "amd,sbtsi",
231	},
232	{ },
233};
234MODULE_DEVICE_TABLE(of, sbtsi_of_match);
235
236static 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
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");