spi: do not deselect other chip-selects

And make sure on reset & init everything is deselected.

Reduces CPU load on a pixhawk cube by almost 1%.

boards/nxp/fmuk66-v3/src/spi.cpp

@@ -300,27 +300,16 @@ __EXPORT int fmuk66_spi_bus_initialize(void)
 
 static inline void kinetis_spixselect(const px4_spi_bus_t *bus, struct spi_dev_s *dev, uint32_t devid, bool selected)
 {
-	int matched_dev_idx = -1;
-
 	for (int i = 0; i < SPI_BUS_MAX_DEVICES; ++i) {
 		if (bus->devices[i].cs_gpio == 0) {
 			break;
 		}
 
 		if (devid == bus->devices[i].devid) {
-			matched_dev_idx = i;
+			// SPI select is active low, so write !selected to select the device
-
+			kinetis_gpiowrite(bus->devices[i].cs_gpio, !selected);
-		} else {
-			// Making sure the other peripherals are not selected
-			kinetis_gpiowrite(bus->devices[i].cs_gpio, 1);
 		}
 	}
-
-	// different devices might use the same CS, so make sure to configure the one we want last
-	if (matched_dev_idx != -1) {
-		// SPI select is active low, so write !selected to select the device
-		kinetis_gpiowrite(bus->devices[matched_dev_idx].cs_gpio, !selected);
-	}
 }
 
 void kinetis_spi0select(FAR struct spi_dev_s *dev, uint32_t devid, bool selected)

boards/nxp/fmurt1062-v1/src/spi.cpp

@@ -241,27 +241,16 @@ __EXPORT int imxrt1062_spi_bus_initialize(void)
 
 static inline void imxrt_spixselect(const px4_spi_bus_t *bus, struct spi_dev_s *dev, uint32_t devid, bool selected)
 {
-	int matched_dev_idx = -1;
-
 	for (int i = 0; i < SPI_BUS_MAX_DEVICES; ++i) {
 		if (bus->devices[i].cs_gpio == 0) {
 			break;
 		}
 
 		if (devid == bus->devices[i].devid) {
-			matched_dev_idx = i;
+			// SPI select is active low, so write !selected to select the device
-
+			imxrt_gpio_write(bus->devices[i].cs_gpio, !selected);
-		} else {
-			// Making sure the other peripherals are not selected
-			imxrt_gpio_write(bus->devices[i].cs_gpio, 1);
 		}
 	}
-
-	// different devices might use the same CS, so make sure to configure the one we want last
-	if (matched_dev_idx != -1) {
-		// SPI select is active low, so write !selected to select the device
-		imxrt_gpio_write(bus->devices[matched_dev_idx].cs_gpio, !selected);
-	}
 }
 
 #if defined(CONFIG_IMXRT_LPSPI1)

platforms/nuttx/src/px4/stm/stm32_common/spi/spi.cpp

@@ -184,27 +184,16 @@ __EXPORT void stm32_spiinitialize()
 
 static inline void stm32_spixselect(const px4_spi_bus_t *bus, struct spi_dev_s *dev, uint32_t devid, bool selected)
 {
-	int matched_dev_idx = -1;
-
 	for (int i = 0; i < SPI_BUS_MAX_DEVICES; ++i) {
 		if (bus->devices[i].cs_gpio == 0) {
 			break;
 		}
 
 		if (devid == bus->devices[i].devid) {
-			matched_dev_idx = i;
+			// SPI select is active low, so write !selected to select the device
-
+			stm32_gpiowrite(bus->devices[i].cs_gpio, !selected);
-		} else {
-			// Making sure the other peripherals are not selected
-			stm32_gpiowrite(bus->devices[i].cs_gpio, 1);
 		}
 	}
-
-	// different devices might use the same CS, so make sure to configure the one we want last
-	if (matched_dev_idx != -1) {
-		// SPI select is active low, so write !selected to select the device
-		stm32_gpiowrite(bus->devices[matched_dev_idx].cs_gpio, !selected);
-	}
 }