drivers/iio/chemical/bme680_spi.c

   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/acpi.h>
   8 #include <linux/module.h>
   9 #include <linux/of.h>
  10 #include <linux/regmap.h>
  11 #include <linux/spi/spi.h>
  12
  13 #include "bme680.h"
  14
  15 struct bme680_spi_bus_context {
  16         struct spi_device *spi;
  17         u8 current_page;
  18 };
  19
  20 /*
  21  * In SPI mode there are only 7 address bits, a "page" register determines
  22  * which part of the 8-bit range is active. This function looks at the address
  23  * and writes the page selection bit if needed
  24  */
  25 static int bme680_regmap_spi_select_page(
  26         struct bme680_spi_bus_context *ctx, u8 reg)
  27 {
  28         struct spi_device *spi = ctx->spi;
  29         int ret;
  30         u8 buf[2];
  31         u8 page = (reg & 0x80) ? 0 : 1; /* Page "1" is low range */
  32
  33         if (page == ctx->current_page)
  34                 return 0;
  35
  36         /*
  37          * Data sheet claims we're only allowed to change bit 4, so we must do
  38          * a read-modify-write on each and every page select
  39          */
  40         buf[0] = BME680_REG_STATUS;
  41         ret = spi_write_then_read(spi, buf, 1, buf + 1, 1);
  42         if (ret < 0) {
  43                 dev_err(&spi->dev, "failed to set page %u\n", page);
  44                 return ret;
  45         }
  46
  47         buf[0] = BME680_REG_STATUS;
  48         if (page)
  49                 buf[1] |= BME680_SPI_MEM_PAGE_BIT;
  50         else
  51                 buf[1] &= ~BME680_SPI_MEM_PAGE_BIT;
  52
  53         ret = spi_write(spi, buf, 2);
  54         if (ret < 0) {
  55                 dev_err(&spi->dev, "failed to set page %u\n", page);
  56                 return ret;
  57         }
  58
  59         ctx->current_page = page;
  60
  61         return 0;
  62 }
  63
  64 static int bme680_regmap_spi_write(void *context, const void *data,
  65                                    size_t count)
  66 {
  67         struct bme680_spi_bus_context *ctx = context;
  68         struct spi_device *spi = ctx->spi;
  69         int ret;
  70         u8 buf[2];
  71
  72         memcpy(buf, data, 2);
  73
  74         ret = bme680_regmap_spi_select_page(ctx, buf[0]);
  75         if (ret)
  76                 return ret;
  77
  78         /*
  79          * The SPI register address (= full register address without bit 7)
  80          * and the write command (bit7 = RW = '0')
  81          */
  82         buf[0] &= ~0x80;
  83
  84         return spi_write(spi, buf, 2);
  85 }
  86
  87 static int bme680_regmap_spi_read(void *context, const void *reg,
  88                                   size_t reg_size, void *val, size_t val_size)
  89 {
  90         struct bme680_spi_bus_context *ctx = context;
  91         struct spi_device *spi = ctx->spi;
  92         int ret;
  93         u8 addr = *(const u8 *)reg;
  94
  95         ret = bme680_regmap_spi_select_page(ctx, addr);
  96         if (ret)
  97                 return ret;
  98
  99         addr |= 0x80; /* bit7 = RW = '1' */
 100
 101         return spi_write_then_read(spi, &addr, 1, val, val_size);
 102 }
 103
 104 static struct regmap_bus bme680_regmap_bus = {
 105         .write = bme680_regmap_spi_write,
 106         .read = bme680_regmap_spi_read,
 107         .reg_format_endian_default = REGMAP_ENDIAN_BIG,
 108         .val_format_endian_default = REGMAP_ENDIAN_BIG,
 109 };
 110
 111 static int bme680_spi_probe(struct spi_device *spi)
 112 {
 113         const struct spi_device_id *id = spi_get_device_id(spi);
 114         struct bme680_spi_bus_context *bus_context;
 115         struct regmap *regmap;
 116         int ret;
 117
 118         spi->bits_per_word = 8;
 119         ret = spi_setup(spi);
 120         if (ret < 0) {
 121                 dev_err(&spi->dev, "spi_setup failed!\n");
 122                 return ret;
 123         }
 124
 125         bus_context = devm_kzalloc(&spi->dev, sizeof(*bus_context), GFP_KERNEL);
 126         if (!bus_context)
 127                 return -ENOMEM;
 128
 129         bus_context->spi = spi;
 130         bus_context->current_page = 0xff; /* Undefined on warm boot */
 131
 132         regmap = devm_regmap_init(&spi->dev, &bme680_regmap_bus,
 133                                   bus_context, &bme680_regmap_config);
 134         if (IS_ERR(regmap)) {
 135                 dev_err(&spi->dev, "Failed to register spi regmap %d\n",
 136                                 (int)PTR_ERR(regmap));
 137                 return PTR_ERR(regmap);
 138         }
 139
 140         return bme680_core_probe(&spi->dev, regmap, id->name);
 141 }
 142
 143 static const struct spi_device_id bme680_spi_id[] = {
 144         {"bme680", 0},
 145         {},
 146 };
 147 MODULE_DEVICE_TABLE(spi, bme680_spi_id);
 148
 149 static const struct acpi_device_id bme680_acpi_match[] = {
 150         {"BME0680", 0},
 151         {},
 152 };
 153 MODULE_DEVICE_TABLE(acpi, bme680_acpi_match);
 154
 155 static const struct of_device_id bme680_of_spi_match[] = {
 156         { .compatible = "bosch,bme680", },
 157         {},
 158 };
 159 MODULE_DEVICE_TABLE(of, bme680_of_spi_match);
 160
 161 static struct spi_driver bme680_spi_driver = {
 162         .driver = {
 163                 .name                   = "bme680_spi",
 164                 .acpi_match_table       = ACPI_PTR(bme680_acpi_match),
 165                 .of_match_table         = bme680_of_spi_match,
 166         },
 167         .probe = bme680_spi_probe,
 168         .id_table = bme680_spi_id,
 169 };
 170 module_spi_driver(bme680_spi_driver);
 171
 172 MODULE_AUTHOR("Himanshu Jha <himanshujha199640@gmail.com>");
 173 MODULE_DESCRIPTION("Bosch BME680 SPI driver");
 174 MODULE_LICENSE("GPL v2");