1// SPDX-License-Identifier: GPL-2.0
2/*
3 * BME680 - SPI Driver
4 *
5 * Copyright (C) 2018 Himanshu Jha <himanshujha199640@gmail.com>
6 */
7#include <linux/mod_devicetable.h>
8#include <linux/module.h>
9#include <linux/regmap.h>
10#include <linux/spi/spi.h>
11
12#include "bme680.h"
13
14struct bme680_spi_bus_context {
15 struct spi_device *spi;
16 u8 current_page;
17};
18
19/*
20 * In SPI mode there are only 7 address bits, a "page" register determines
21 * which part of the 8-bit range is active. This function looks at the address
22 * and writes the page selection bit if needed
23 */
24static int bme680_regmap_spi_select_page(
25 struct bme680_spi_bus_context *ctx, u8 reg)
26{
27 struct spi_device *spi = ctx->spi;
28 int ret;
29 u8 buf[2];
30 u8 page = (reg & 0x80) ? 0 : 1; /* Page "1" is low range */
31
32 if (page == ctx->current_page)
33 return 0;
34
35 /*
36 * Data sheet claims we're only allowed to change bit 4, so we must do
37 * a read-modify-write on each and every page select
38 */
39 buf[0] = BME680_REG_STATUS;
40 ret = spi_write_then_read(spi, txbuf: buf, n_tx: 1, rxbuf: buf + 1, n_rx: 1);
41 if (ret < 0) {
42 dev_err(&spi->dev, "failed to set page %u\n", page);
43 return ret;
44 }
45
46 buf[0] = BME680_REG_STATUS;
47 if (page)
48 buf[1] |= BME680_SPI_MEM_PAGE_BIT;
49 else
50 buf[1] &= ~BME680_SPI_MEM_PAGE_BIT;
51
52 ret = spi_write(spi, buf, len: 2);
53 if (ret < 0) {
54 dev_err(&spi->dev, "failed to set page %u\n", page);
55 return ret;
56 }
57
58 ctx->current_page = page;
59
60 return 0;
61}
62
63static int bme680_regmap_spi_write(void *context, const void *data,
64 size_t count)
65{
66 struct bme680_spi_bus_context *ctx = context;
67 struct spi_device *spi = ctx->spi;
68 int ret;
69 u8 buf[2];
70
71 memcpy(buf, data, 2);
72
73 ret = bme680_regmap_spi_select_page(ctx, reg: buf[0]);
74 if (ret)
75 return ret;
76
77 /*
78 * The SPI register address (= full register address without bit 7)
79 * and the write command (bit7 = RW = '0')
80 */
81 buf[0] &= ~0x80;
82
83 return spi_write(spi, buf, len: 2);
84}
85
86static int bme680_regmap_spi_read(void *context, const void *reg,
87 size_t reg_size, void *val, size_t val_size)
88{
89 struct bme680_spi_bus_context *ctx = context;
90 struct spi_device *spi = ctx->spi;
91 int ret;
92 u8 addr = *(const u8 *)reg;
93
94 ret = bme680_regmap_spi_select_page(ctx, reg: addr);
95 if (ret)
96 return ret;
97
98 addr |= 0x80; /* bit7 = RW = '1' */
99
100 return spi_write_then_read(spi, txbuf: &addr, n_tx: 1, rxbuf: val, n_rx: val_size);
101}
102
103static struct regmap_bus bme680_regmap_bus = {
104 .write = bme680_regmap_spi_write,
105 .read = bme680_regmap_spi_read,
106 .reg_format_endian_default = REGMAP_ENDIAN_BIG,
107 .val_format_endian_default = REGMAP_ENDIAN_BIG,
108};
109
110static int bme680_spi_probe(struct spi_device *spi)
111{
112 const struct spi_device_id *id = spi_get_device_id(sdev: spi);
113 struct bme680_spi_bus_context *bus_context;
114 struct regmap *regmap;
115 int ret;
116
117 spi->bits_per_word = 8;
118 ret = spi_setup(spi);
119 if (ret < 0) {
120 dev_err(&spi->dev, "spi_setup failed!\n");
121 return ret;
122 }
123
124 bus_context = devm_kzalloc(dev: &spi->dev, size: sizeof(*bus_context), GFP_KERNEL);
125 if (!bus_context)
126 return -ENOMEM;
127
128 bus_context->spi = spi;
129 bus_context->current_page = 0xff; /* Undefined on warm boot */
130
131 regmap = devm_regmap_init(&spi->dev, &bme680_regmap_bus,
132 bus_context, &bme680_regmap_config);
133 if (IS_ERR(ptr: regmap)) {
134 dev_err(&spi->dev, "Failed to register spi regmap %ld\n", PTR_ERR(regmap));
135 return PTR_ERR(ptr: regmap);
136 }
137
138 return bme680_core_probe(dev: &spi->dev, regmap, name: id->name);
139}
140
141static const struct spi_device_id bme680_spi_id[] = {
142 {"bme680", 0},
143 {},
144};
145MODULE_DEVICE_TABLE(spi, bme680_spi_id);
146
147static const struct of_device_id bme680_of_spi_match[] = {
148 { .compatible = "bosch,bme680", },
149 {},
150};
151MODULE_DEVICE_TABLE(of, bme680_of_spi_match);
152
153static struct spi_driver bme680_spi_driver = {
154 .driver = {
155 .name = "bme680_spi",
156 .of_match_table = bme680_of_spi_match,
157 },
158 .probe = bme680_spi_probe,
159 .id_table = bme680_spi_id,
160};
161module_spi_driver(bme680_spi_driver);
162
163MODULE_AUTHOR("Himanshu Jha <himanshujha199640@gmail.com>");
164MODULE_DESCRIPTION("Bosch BME680 SPI driver");
165MODULE_LICENSE("GPL v2");
166MODULE_IMPORT_NS(IIO_BME680);
167

source code of linux/drivers/iio/chemical/bme680_spi.c