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/module.h>
8 #include <linux/of.h>
9 #include <linux/regmap.h>
10 #include <linux/spi/spi.h>
11 
12 #include "bme680.h"
13 
14 struct 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  */
bme680_regmap_spi_select_page(struct bme680_spi_bus_context * ctx,u8 reg)24 static 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, buf, 1, buf + 1, 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, 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 
bme680_regmap_spi_write(void * context,const void * data,size_t count)63 static 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, 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, 2);
84 }
85 
bme680_regmap_spi_read(void * context,const void * reg,size_t reg_size,void * val,size_t val_size)86 static 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, addr);
95 	if (ret)
96 		return ret;
97 
98 	addr |= 0x80; /* bit7 = RW = '1' */
99 
100 	return spi_write_then_read(spi, &addr, 1, val, val_size);
101 }
102 
103 static 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 
bme680_spi_probe(struct spi_device * spi)110 static int bme680_spi_probe(struct spi_device *spi)
111 {
112 	const struct spi_device_id *id = spi_get_device_id(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(&spi->dev, 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(regmap)) {
134 		dev_err(&spi->dev, "Failed to register spi regmap %ld\n", PTR_ERR(regmap));
135 		return PTR_ERR(regmap);
136 	}
137 
138 	return bme680_core_probe(&spi->dev, regmap, id->name);
139 }
140 
141 static const struct spi_device_id bme680_spi_id[] = {
142 	{"bme680", 0},
143 	{},
144 };
145 MODULE_DEVICE_TABLE(spi, bme680_spi_id);
146 
147 static const struct of_device_id bme680_of_spi_match[] = {
148 	{ .compatible = "bosch,bme680", },
149 	{},
150 };
151 MODULE_DEVICE_TABLE(of, bme680_of_spi_match);
152 
153 static 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 };
161 module_spi_driver(bme680_spi_driver);
162 
163 MODULE_AUTHOR("Himanshu Jha <himanshujha199640@gmail.com>");
164 MODULE_DESCRIPTION("Bosch BME680 SPI driver");
165 MODULE_LICENSE("GPL v2");
166