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/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");