1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * Sensirion SCD30 carbon dioxide sensor i2c driver
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * Copyright (c) 2020 Tomasz Duszynski <tomasz.duszynski@octakon.com>
6*4882a593Smuzhiyun *
7*4882a593Smuzhiyun * I2C slave address: 0x61
8*4882a593Smuzhiyun */
9*4882a593Smuzhiyun #include <linux/crc8.h>
10*4882a593Smuzhiyun #include <linux/device.h>
11*4882a593Smuzhiyun #include <linux/errno.h>
12*4882a593Smuzhiyun #include <linux/i2c.h>
13*4882a593Smuzhiyun #include <linux/mod_devicetable.h>
14*4882a593Smuzhiyun #include <linux/module.h>
15*4882a593Smuzhiyun #include <linux/types.h>
16*4882a593Smuzhiyun #include <asm/unaligned.h>
17*4882a593Smuzhiyun
18*4882a593Smuzhiyun #include "scd30.h"
19*4882a593Smuzhiyun
20*4882a593Smuzhiyun #define SCD30_I2C_MAX_BUF_SIZE 18
21*4882a593Smuzhiyun #define SCD30_I2C_CRC8_POLYNOMIAL 0x31
22*4882a593Smuzhiyun
23*4882a593Smuzhiyun static u16 scd30_i2c_cmd_lookup_tbl[] = {
24*4882a593Smuzhiyun [CMD_START_MEAS] = 0x0010,
25*4882a593Smuzhiyun [CMD_STOP_MEAS] = 0x0104,
26*4882a593Smuzhiyun [CMD_MEAS_INTERVAL] = 0x4600,
27*4882a593Smuzhiyun [CMD_MEAS_READY] = 0x0202,
28*4882a593Smuzhiyun [CMD_READ_MEAS] = 0x0300,
29*4882a593Smuzhiyun [CMD_ASC] = 0x5306,
30*4882a593Smuzhiyun [CMD_FRC] = 0x5204,
31*4882a593Smuzhiyun [CMD_TEMP_OFFSET] = 0x5403,
32*4882a593Smuzhiyun [CMD_FW_VERSION] = 0xd100,
33*4882a593Smuzhiyun [CMD_RESET] = 0xd304,
34*4882a593Smuzhiyun };
35*4882a593Smuzhiyun
36*4882a593Smuzhiyun DECLARE_CRC8_TABLE(scd30_i2c_crc8_tbl);
37*4882a593Smuzhiyun
scd30_i2c_xfer(struct scd30_state * state,char * txbuf,int txsize,char * rxbuf,int rxsize)38*4882a593Smuzhiyun static int scd30_i2c_xfer(struct scd30_state *state, char *txbuf, int txsize,
39*4882a593Smuzhiyun char *rxbuf, int rxsize)
40*4882a593Smuzhiyun {
41*4882a593Smuzhiyun struct i2c_client *client = to_i2c_client(state->dev);
42*4882a593Smuzhiyun int ret;
43*4882a593Smuzhiyun
44*4882a593Smuzhiyun /*
45*4882a593Smuzhiyun * repeated start is not supported hence instead of sending two i2c
46*4882a593Smuzhiyun * messages in a row we send one by one
47*4882a593Smuzhiyun */
48*4882a593Smuzhiyun ret = i2c_master_send(client, txbuf, txsize);
49*4882a593Smuzhiyun if (ret < 0)
50*4882a593Smuzhiyun return ret;
51*4882a593Smuzhiyun if (ret != txsize)
52*4882a593Smuzhiyun return -EIO;
53*4882a593Smuzhiyun
54*4882a593Smuzhiyun if (!rxbuf)
55*4882a593Smuzhiyun return 0;
56*4882a593Smuzhiyun
57*4882a593Smuzhiyun ret = i2c_master_recv(client, rxbuf, rxsize);
58*4882a593Smuzhiyun if (ret < 0)
59*4882a593Smuzhiyun return ret;
60*4882a593Smuzhiyun if (ret != rxsize)
61*4882a593Smuzhiyun return -EIO;
62*4882a593Smuzhiyun
63*4882a593Smuzhiyun return 0;
64*4882a593Smuzhiyun }
65*4882a593Smuzhiyun
scd30_i2c_command(struct scd30_state * state,enum scd30_cmd cmd,u16 arg,void * response,int size)66*4882a593Smuzhiyun static int scd30_i2c_command(struct scd30_state *state, enum scd30_cmd cmd, u16 arg,
67*4882a593Smuzhiyun void *response, int size)
68*4882a593Smuzhiyun {
69*4882a593Smuzhiyun char buf[SCD30_I2C_MAX_BUF_SIZE];
70*4882a593Smuzhiyun char *rsp = response;
71*4882a593Smuzhiyun int i, ret;
72*4882a593Smuzhiyun char crc;
73*4882a593Smuzhiyun
74*4882a593Smuzhiyun put_unaligned_be16(scd30_i2c_cmd_lookup_tbl[cmd], buf);
75*4882a593Smuzhiyun i = 2;
76*4882a593Smuzhiyun
77*4882a593Smuzhiyun if (rsp) {
78*4882a593Smuzhiyun /* each two bytes are followed by a crc8 */
79*4882a593Smuzhiyun size += size / 2;
80*4882a593Smuzhiyun } else {
81*4882a593Smuzhiyun put_unaligned_be16(arg, buf + i);
82*4882a593Smuzhiyun crc = crc8(scd30_i2c_crc8_tbl, buf + i, 2, CRC8_INIT_VALUE);
83*4882a593Smuzhiyun i += 2;
84*4882a593Smuzhiyun buf[i] = crc;
85*4882a593Smuzhiyun i += 1;
86*4882a593Smuzhiyun
87*4882a593Smuzhiyun /* commands below don't take an argument */
88*4882a593Smuzhiyun if ((cmd == CMD_STOP_MEAS) || (cmd == CMD_RESET))
89*4882a593Smuzhiyun i -= 3;
90*4882a593Smuzhiyun }
91*4882a593Smuzhiyun
92*4882a593Smuzhiyun ret = scd30_i2c_xfer(state, buf, i, buf, size);
93*4882a593Smuzhiyun if (ret)
94*4882a593Smuzhiyun return ret;
95*4882a593Smuzhiyun
96*4882a593Smuzhiyun /* validate received data and strip off crc bytes */
97*4882a593Smuzhiyun for (i = 0; i < size; i += 3) {
98*4882a593Smuzhiyun crc = crc8(scd30_i2c_crc8_tbl, buf + i, 2, CRC8_INIT_VALUE);
99*4882a593Smuzhiyun if (crc != buf[i + 2]) {
100*4882a593Smuzhiyun dev_err(state->dev, "data integrity check failed\n");
101*4882a593Smuzhiyun return -EIO;
102*4882a593Smuzhiyun }
103*4882a593Smuzhiyun
104*4882a593Smuzhiyun *rsp++ = buf[i];
105*4882a593Smuzhiyun *rsp++ = buf[i + 1];
106*4882a593Smuzhiyun }
107*4882a593Smuzhiyun
108*4882a593Smuzhiyun return 0;
109*4882a593Smuzhiyun }
110*4882a593Smuzhiyun
scd30_i2c_probe(struct i2c_client * client)111*4882a593Smuzhiyun static int scd30_i2c_probe(struct i2c_client *client)
112*4882a593Smuzhiyun {
113*4882a593Smuzhiyun if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
114*4882a593Smuzhiyun return -EOPNOTSUPP;
115*4882a593Smuzhiyun
116*4882a593Smuzhiyun crc8_populate_msb(scd30_i2c_crc8_tbl, SCD30_I2C_CRC8_POLYNOMIAL);
117*4882a593Smuzhiyun
118*4882a593Smuzhiyun return scd30_probe(&client->dev, client->irq, client->name, NULL, scd30_i2c_command);
119*4882a593Smuzhiyun }
120*4882a593Smuzhiyun
121*4882a593Smuzhiyun static const struct of_device_id scd30_i2c_of_match[] = {
122*4882a593Smuzhiyun { .compatible = "sensirion,scd30" },
123*4882a593Smuzhiyun { }
124*4882a593Smuzhiyun };
125*4882a593Smuzhiyun MODULE_DEVICE_TABLE(of, scd30_i2c_of_match);
126*4882a593Smuzhiyun
127*4882a593Smuzhiyun static struct i2c_driver scd30_i2c_driver = {
128*4882a593Smuzhiyun .driver = {
129*4882a593Smuzhiyun .name = KBUILD_MODNAME,
130*4882a593Smuzhiyun .of_match_table = scd30_i2c_of_match,
131*4882a593Smuzhiyun .pm = &scd30_pm_ops,
132*4882a593Smuzhiyun },
133*4882a593Smuzhiyun .probe_new = scd30_i2c_probe,
134*4882a593Smuzhiyun };
135*4882a593Smuzhiyun module_i2c_driver(scd30_i2c_driver);
136*4882a593Smuzhiyun
137*4882a593Smuzhiyun MODULE_AUTHOR("Tomasz Duszynski <tomasz.duszynski@octakon.com>");
138*4882a593Smuzhiyun MODULE_DESCRIPTION("Sensirion SCD30 carbon dioxide sensor i2c driver");
139*4882a593Smuzhiyun MODULE_LICENSE("GPL v2");
140