iio: pressure: bmp280: add SPI interface driver

This patch mimics the SPI functionality found in the misc driver in
drivers/misc/bh085-spi.c to make it possible to reuse the existing
BMP280/BMP180/BMP085 driver with all clients of the other driver.
The adoption is straight-forward since like the other driver, it is
a simple matter of using regmap.

This driver is also so obviously inspired/copied from the old misc
driver in drivers/misc/bmp085.c that I just took the liberty to
add in the authors of the other drivers + self in the core driver
file.

The MISC driver also supports a variant named "BMP181" so include
that here to be complete in comparison to the old driver.

The bus mapping code for SPI was written by Akinobu Mita.
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Tested-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/pressure/Kconfig

@@ -7,17 +7,20 @@ menu "Pressure sensors"
 
 config BMP280
 	tristate "Bosch Sensortec BMP180/BMP280 pressure sensor I2C driver"
-	depends on I2C
+	depends on (I2C || SPI_MASTER)
 	depends on !(BMP085_I2C=y || BMP085_I2C=m)
+	depends on !(BMP085_SPI=y || BMP085_SPI=m)
 	select REGMAP
 	select BMP280_I2C if (I2C)
+	select BMP280_SPI if (SPI_MASTER)
 	help
 	  Say yes here to build support for Bosch Sensortec BMP180 and BMP280
 	  pressure and temperature sensors. Also supports the BE280 with
 	  an additional humidity sensor channel.
 
-	  To compile this driver as a module, choose M here: the modules
-	  will be called bmp280-i2c and bmp280.
+	  To compile this driver as a module, choose M here: the core module
+	  will be called bmp280 and you will also get bmp280-i2c for I2C
+	  and/or bmp280-spi for SPI support.
 
 config BMP280_I2C
 	tristate
@@ -25,6 +28,12 @@ config BMP280_I2C
 	depends on I2C
 	select REGMAP_I2C
 
+config BMP280_SPI
+	tristate
+	depends on BMP280
+	depends on SPI_MASTER
+	select REGMAP
+
 config HID_SENSOR_PRESS
 	depends on HID_SENSOR_HUB
 	select IIO_BUFFER

drivers/iio/pressure/Makefile

@@ -6,6 +6,7 @@
 obj-$(CONFIG_BMP280) += bmp280.o
 bmp280-objs := bmp280-core.o bmp280-regmap.o
 obj-$(CONFIG_BMP280_I2C) += bmp280-i2c.o
+obj-$(CONFIG_BMP280_SPI) += bmp280-spi.o
 obj-$(CONFIG_HID_SENSOR_PRESS)   += hid-sensor-press.o
 obj-$(CONFIG_HP03) += hp03.o
 obj-$(CONFIG_MPL115) += mpl115.o

drivers/iio/pressure/bmp280-core.c

 /*
+ * Copyright (c) 2010 Christoph Mair <christoph.mair@gmail.com>
+ * Copyright (c) 2012 Bosch Sensortec GmbH
+ * Copyright (c) 2012 Unixphere AB
  * Copyright (c) 2014 Intel Corporation
+ * Copyright (c) 2016 Linus Walleij <linus.walleij@linaro.org>
  *
  * Driver for Bosch Sensortec BMP180 and BMP280 digital pressure sensor.
  *

drivers/iio/pressure/bmp280-spi.c

+/*
+ * SPI interface for the BMP280 driver
+ *
+ * Inspired by the older BMP085 driver drivers/misc/bmp085-spi.c
+ */
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+#include <linux/err.h>
+#include <linux/regmap.h>
+
+#include "bmp280.h"
+
+static int bmp280_regmap_spi_write(void *context, const void *data,
+                                   size_t count)
+{
+	struct device *dev = context;
+	struct spi_device *spi = to_spi_device(dev);
+	u8 buf[2];
+
+	memcpy(buf, data, 2);
+	/*
+	 * The SPI register address (= full register address without bit 7) and
+	 * the write command (bit7 = RW = '0')
+	 */
+	buf[0] &= ~0x80;
+
+	return spi_write_then_read(spi, buf, 2, NULL, 0);
+}
+
+static int bmp280_regmap_spi_read(void *context, const void *reg,
+                                  size_t reg_size, void *val, size_t val_size)
+{
+	struct device *dev = context;
+	struct spi_device *spi = to_spi_device(dev);
+
+	return spi_write_then_read(spi, reg, reg_size, val, val_size);
+}
+
+static struct regmap_bus bmp280_regmap_bus = {
+	.write = bmp280_regmap_spi_write,
+	.read = bmp280_regmap_spi_read,
+	.reg_format_endian_default = REGMAP_ENDIAN_BIG,
+	.val_format_endian_default = REGMAP_ENDIAN_BIG,
+};
+
+static int bmp280_spi_probe(struct spi_device *spi)
+{
+	const struct spi_device_id *id = spi_get_device_id(spi);
+	struct regmap *regmap;
+	const struct regmap_config *regmap_config;
+	int ret;
+
+	spi->bits_per_word = 8;
+	ret = spi_setup(spi);
+	if (ret < 0) {
+		dev_err(&spi->dev, "spi_setup failed!\n");
+		return ret;
+	}
+
+	switch (id->driver_data) {
+	case BMP180_CHIP_ID:
+		regmap_config = &bmp180_regmap_config;
+		break;
+	case BMP280_CHIP_ID:
+	case BME280_CHIP_ID:
+		regmap_config = &bmp280_regmap_config;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	regmap = devm_regmap_init(&spi->dev,
+				  &bmp280_regmap_bus,
+				  &spi->dev,
+				  regmap_config);
+	if (IS_ERR(regmap)) {
+		dev_err(&spi->dev, "failed to allocate register map\n");
+		return PTR_ERR(regmap);
+	}
+
+	return bmp280_common_probe(&spi->dev,
+				   regmap,
+				   id->driver_data,
+				   id->name);
+}
+
+static int bmp280_spi_remove(struct spi_device *spi)
+{
+	return bmp280_common_remove(&spi->dev);
+}
+
+static const struct of_device_id bmp280_of_spi_match[] = {
+	{ .compatible = "bosch,bmp085", },
+	{ .compatible = "bosch,bmp180", },
+	{ .compatible = "bosch,bmp181", },
+	{ .compatible = "bosch,bmp280", },
+	{ .compatible = "bosch,bme280", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, bmp280_of_spi_match);
+
+static const struct spi_device_id bmp280_spi_id[] = {
+	{ "bmp180", BMP180_CHIP_ID },
+	{ "bmp181", BMP180_CHIP_ID },
+	{ "bmp280", BMP280_CHIP_ID },
+	{ "bme280", BME280_CHIP_ID },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, bmp280_spi_id);
+
+static struct spi_driver bmp280_spi_driver = {
+	.driver = {
+		.name = "bmp280",
+		.of_match_table = bmp280_of_spi_match,
+	},
+	.id_table = bmp280_spi_id,
+	.probe = bmp280_spi_probe,
+	.remove = bmp280_spi_remove,
+};
+module_spi_driver(bmp280_spi_driver);
+
+MODULE_DESCRIPTION("BMP280 SPI bus driver");
+MODULE_LICENSE("GPL");