ms5611: lower SPI clock 20 MHz -> 16 MHz

- this was necessary to get the secondary ms5611 working reliably on a
particular CubeOrange
 - the sensor is transferring very little data, so lowering the speed by
default everywhere is harmless

src/drivers/barometer/ms5611/CMakeLists.txt

@@ -35,7 +35,6 @@ px4_add_module(
 	MODULE drivers__barometer__ms5611
 	MAIN ms5611
 	COMPILE_FLAGS
-		-Wno-cast-align # TODO: fix and enable
 	SRCS
 		ms5611_spi.cpp
 		ms5611_i2c.cpp

src/drivers/barometer/ms5611/ms5611_main.cpp

@@ -107,7 +107,7 @@ extern "C" int ms5611_main(int argc, char *argv[])
 #else
 	BusCLIArguments cli {false, true};
 #endif
-	cli.default_spi_frequency = 20 * 1000 * 1000;
+	cli.default_spi_frequency = 16 * 1000 * 1000;
 	uint16_t dev_type_driver = DRV_BARO_DEVTYPE_MS5611;
 
 	while ((ch = cli.getOpt(argc, argv, "T:")) != EOF) {

src/drivers/barometer/ms5611/ms5611_spi.cpp

@@ -115,27 +115,32 @@ MS5611_SPI::init()
 
 	if (ret != OK) {
 		PX4_DEBUG("SPI init failed");
-		goto out;
+		return PX4_ERROR;
 	}
 
-	/* send reset command */
-	ret = _reset();
+	// reset and read PROM (try up to 3 times)
+	for (int i = 0; i < 3; i++) {
+		/* send reset command */
+		ret = _reset();
 
-	if (ret != OK) {
-		PX4_DEBUG("reset failed");
-		goto out;
+		if (ret != OK) {
+			PX4_DEBUG("reset failed");
+			continue;
+		}
+
+		/* read PROM */
+		ret = _read_prom();
+
+		if (ret == OK) {
+			return PX4_OK;
+
+		} else {
+			PX4_DEBUG("prom readout failed");
+			continue;
+		}
 	}
 
-	/* read PROM */
-	ret = _read_prom();
-
-	if (ret != OK) {
-		PX4_DEBUG("prom readout failed");
-		goto out;
-	}
-
-out:
-	return ret;
+	return PX4_ERROR;
 }
 
 int