driver/sensor: lis2mdl: handle SPI 4-wires mode selection

The LIS2MDL supports SPI half duplex mode with a single data line
by default (3-wire), but it might configured to switch to standard
full duplex mode (4-wire).

Signed-off-by: Armando Visconti <armando.visconti@st.com>

drivers/sensor/lis2mdl/Kconfig

@@ -53,4 +53,8 @@ config LIS2MDL_MAG_ODR_RUNTIME
 	bool "Set magnetometer sampling frequency (ODR) at runtime (default: 10 Hz)"
 	default y
 
+config LIS2MDL_SPI_FULL_DUPLEX
+	bool "Enable SPI 4wire mode (separated MISO and MOSI lines)"
+	depends on SPI
+
 endif # LIS2MDL

drivers/sensor/lis2mdl/lis2mdl.c

@@ -310,6 +310,13 @@ static int lis2mdl_init(struct device *dev)
 
 	k_busy_wait(100);
 
+#if CONFIG_LIS2MDL_SPI_FULL_DUPLEX
+	/* After s/w reset set SPI 4wires again if the case */
+	if (lis2mdl_spi_mode_set(lis2mdl->ctx, LIS2MDL_SPI_4_WIRE) < 0) {
+		return -EIO;
+	}
+#endif
+
 	/* enable BDU */
 	if (lis2mdl_block_data_update_set(lis2mdl->ctx, PROPERTY_ENABLE) < 0) {
 		LOG_DBG("setting bdu failed\n");

drivers/sensor/lis2mdl/lis2mdl_spi.c

@@ -122,6 +122,13 @@ int lis2mdl_spi_init(struct device *dev)
 		cfg->gpio_cs_port, cfg->cs_gpio);
 #endif
 
+#if CONFIG_LIS2MDL_SPI_FULL_DUPLEX
+	/* Set SPI 4wires */
+	if (lis2mdl_spi_mode_set(data->ctx, LIS2MDL_SPI_4_WIRE) < 0) {
+		return -EIO;
+	}
+#endif
+
 	return 0;
 }
 #endif /* DT_ST_LIS2MDL_BUS_SPI */