[PATCH 2/2] drivers: iio: pressure: Fixes BMP38x and BMP390 SPI support

[Vasileios Amoiridis <vassilisamir@gmail.com>]

According to the datasheet of BMP38x and BMP390 devices, for an SPI
read operation the first byte that is returned needs to be dropped,
and the rest of the bytes are the actual data returned from the
sensor.

Fixes: 8d329309184d ("iio: pressure: bmp280: Add support for BMP380 sensor family")
Signed-off-by: Vasileios Amoiridis <vassilisamir@gmail.com>
---
 drivers/iio/pressure/bmp280-spi.c | 50 ++++++++++++++++++++++++++++++-
 1 file changed, 49 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/pressure/bmp280-spi.c b/drivers/iio/pressure/bmp280-spi.c
index fd7ec6a5bca3..7ea79fe57cfd 100644
--- a/drivers/iio/pressure/bmp280-spi.c
+++ b/drivers/iio/pressure/bmp280-spi.c
@@ -4,6 +4,7 @@
  *
  * Inspired by the older BMP085 driver drivers/misc/bmp085-spi.c
  */
+#include <linux/bits.h>
 #include <linux/err.h>
 #include <linux/module.h>
 #include <linux/regmap.h>
@@ -36,6 +37,34 @@ 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 rx_buf[4];
+	ssize_t status;
+
+	/*
+	 * Maximum number of consecutive bytes read for a temperature or
+	 * pressure measurement is 3.
+	 */
+	if (val_size > 3)
+		return -EINVAL;
+
+	/*
+	 * According to the BMP3xx datasheets, for a basic SPI read opertion,
+	 * the first byte needs to be dropped and the rest are the requested
+	 * data.
+	 */
+	status = spi_write_then_read(spi, reg, 1, rx_buf, val_size + 1);
+	if (status)
+		return status;
+
+	memcpy(val, rx_buf + 1, val_size);
+
+	return 0;
+}
+
 static struct regmap_bus bmp280_regmap_bus = {
 	.write = bmp280_regmap_spi_write,
 	.read = bmp280_regmap_spi_read,
@@ -43,10 +72,19 @@ 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,
+	.read_flag_mask = BIT(7),
+	.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;
 
@@ -59,8 +97,18 @@ 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)) {
-- 
2.25.1