[PATCH] drivers: iio: pressure: Add SPI support for BMP38x and BMP390

[Vasileios Amoiridis <vassilisamir@gmail.com>]

According to the datasheet of BMP38x and BMP390 devices, in SPI
operation, the first byte that returns after a read operation is
garbage and it needs to be dropped and return the rest of the
bytes.

Signed-off-by: Vasileios Amoiridis <vassilisamir@gmail.com>
---
 drivers/iio/pressure/bmp280-spi.c | 47 ++++++++++++++++++++++++++++++-
 drivers/iio/pressure/bmp280.h     |  2 ++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/pressure/bmp280-spi.c b/drivers/iio/pressure/bmp280-spi.c
index 433d6fac83c4..c4b4a5d67f94 100644
--- a/drivers/iio/pressure/bmp280-spi.c
+++ b/drivers/iio/pressure/bmp280-spi.c
@@ -35,6 +35,32 @@ static int bmp280_regmap_spi_read(void *context, const void *reg,
 	return spi_write_then_read(spi, reg, reg_size, val, val_size);
 }
 
+static int bmp380_regmap_spi_read(void *context, const void *reg,
+				  size_t reg_size, void *val, size_t val_size)
+{
+	struct spi_device *spi = to_spi_device(context);
+	u8 ret[BMP380_SPI_MAX_REG_COUNT_READ + 1];
+	ssize_t status;
+	u8 buf;
+
+	memcpy(&buf, reg, reg_size);
+	buf |= 0x80;
+
+	/*
+	 * According to the BMP380, BMP388, BMP390 datasheets, for a basic
+	 * read operation, after the write is done, 2 bytes are received and
+	 * the first one has to be dropped. The 2nd one is the requested
+	 * value.
+	 */
+	status = spi_write_then_read(spi, &buf, 1, ret, val_size + 1);
+	if (status)
+		return status;
+
+	memcpy(val, ret + 1, val_size);
+
+	return 0;
+}
+
 static struct regmap_bus bmp280_regmap_bus = {
 	.write = bmp280_regmap_spi_write,
 	.read = bmp280_regmap_spi_read,
@@ -42,10 +68,18 @@ static struct regmap_bus bmp280_regmap_bus = {
 	.val_format_endian_default = REGMAP_ENDIAN_BIG,
 };
 
+static struct regmap_bus bmp380_regmap_bus = {
+	.write = bmp280_regmap_spi_write,
+	.read = bmp380_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);
 	const struct bmp280_chip_info *chip_info;
+	struct regmap_bus *bmp_regmap_bus;
 	struct regmap *regmap;
 	int ret;
 
@@ -58,8 +92,19 @@ static int bmp280_spi_probe(struct spi_device *spi)
 
 	chip_info = spi_get_device_match_data(spi);
 
+	switch (chip_info->chip_id[0]) {
+	case BMP380_CHIP_ID:
+	case BMP390_CHIP_ID:
+		bmp_regmap_bus = &bmp380_regmap_bus;
+		break;
+	default:
+		bmp_regmap_bus = &bmp280_regmap_bus;
+		break;
+	}
+
+
 	regmap = devm_regmap_init(&spi->dev,
-				  &bmp280_regmap_bus,
+				  bmp_regmap_bus,
 				  &spi->dev,
 				  chip_info->regmap_config);
 	if (IS_ERR(regmap)) {
diff --git a/drivers/iio/pressure/bmp280.h b/drivers/iio/pressure/bmp280.h
index 4012387d7956..ca482b7e4295 100644
--- a/drivers/iio/pressure/bmp280.h
+++ b/drivers/iio/pressure/bmp280.h
@@ -191,6 +191,8 @@
 #define BMP380_TEMP_SKIPPED		0x800000
 #define BMP380_PRESS_SKIPPED		0x800000
 
+#define BMP380_SPI_MAX_REG_COUNT_READ   3
+
 /* BMP280 specific registers */
 #define BMP280_REG_HUMIDITY_LSB		0xFE
 #define BMP280_REG_HUMIDITY_MSB		0xFD
-- 
2.25.1