iio: accel: st_accel: add SPI-3wire support

Add SPI Serial Interface Mode (SIM) register information
in st_sensor_settings look up table to support devices
(like LSM303AGR accel sensor) that allow just SPI-3wire
communication mode. SIM mode has to be configured before any
other operation since it is not enabled by default and the driver
is not able to read without that configuration

Whilst a fairly substantial patch, the actual logic is simple and it
is better to have the generic fix than a band aid.

Fixes: ddc05fa28606 (iio: st-accel: add support for lsm303agr accel)
Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@st.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/drivers/iio/common/st_sensors/st_sensors_core.c b/drivers/iio/common/st_sensors/st_sensors_core.c
index 79c8c7cd70d5..6e6a1ecc99dd 100644
--- a/drivers/iio/common/st_sensors/st_sensors_core.c
+++ b/drivers/iio/common/st_sensors/st_sensors_core.c
@@ -550,6 +550,31 @@ out:
 }
 EXPORT_SYMBOL(st_sensors_read_info_raw);
 
+static int st_sensors_init_interface_mode(struct iio_dev *indio_dev,
+			const struct st_sensor_settings *sensor_settings)
+{
+	struct st_sensor_data *sdata = iio_priv(indio_dev);
+	struct device_node *np = sdata->dev->of_node;
+	struct st_sensors_platform_data *pdata;
+
+	pdata = (struct st_sensors_platform_data *)sdata->dev->platform_data;
+	if (((np && of_property_read_bool(np, "spi-3wire")) ||
+	     (pdata && pdata->spi_3wire)) && sensor_settings->sim.addr) {
+		int err;
+
+		err = sdata->tf->write_byte(&sdata->tb, sdata->dev,
+					    sensor_settings->sim.addr,
+					    sensor_settings->sim.value);
+		if (err < 0) {
+			dev_err(&indio_dev->dev,
+				"failed to init interface mode\n");
+			return err;
+		}
+	}
+
+	return 0;
+}
+
 int st_sensors_check_device_support(struct iio_dev *indio_dev,
 			int num_sensors_list,
 			const struct st_sensor_settings *sensor_settings)
@@ -574,6 +599,10 @@ int st_sensors_check_device_support(struct iio_dev *indio_dev,
 		return -ENODEV;
 	}
 
+	err = st_sensors_init_interface_mode(indio_dev, &sensor_settings[i]);
+	if (err < 0)
+		return err;
+
 	if (sensor_settings[i].wai_addr) {
 		err = sdata->tf->read_byte(&sdata->tb, sdata->dev,
 					   sensor_settings[i].wai_addr, &wai);