[4.4 BackPort] Save/Restore SCK pin state when SPI is stopped and started before transaction

libraries/AP_HAL_ChibiOS/SPIDevice.cpp

@@ -69,6 +69,7 @@ static const struct SPIDriverInfo {
     uint8_t busid; // used for device IDs in parameters
     uint8_t dma_channel_rx;
     uint8_t dma_channel_tx;
+    ioline_t sck_line;
 } spi_devices[] = { HAL_SPI_BUS_LIST };
 
 // device list comes from hwdef.dat
@@ -86,6 +87,10 @@ SPIBus::SPIBus(uint8_t _bus) :
                                 FUNCTOR_BIND_MEMBER(&SPIBus::dma_allocate, void, Shared_DMA *),
                                 FUNCTOR_BIND_MEMBER(&SPIBus::dma_deallocate, void, Shared_DMA *));
 
+    // remember the SCK line for stop_peripheral()/start_peripheral()
+#if HAL_SPI_SCK_SAVE_RESTORE
+    sck_mode = palReadLineMode(spi_devices[bus].sck_line);
+#endif
 }
 
 /*
@@ -103,10 +108,7 @@ void SPIBus::dma_deallocate(Shared_DMA *ctx)
 {
     chMtxLock(&dma_lock);
     // another non-SPI peripheral wants one of our DMA channels
-    if (spi_started) {
-        spiStop(spi_devices[bus].driver);
-        spi_started = false;
-    }
+    stop_peripheral();
     chMtxUnlock(&dma_lock);
 }
 
@@ -339,6 +341,48 @@ bool SPIDevice::adjust_periodic_callback(AP_HAL::Device::PeriodicHandle h, uint3
     return bus.adjust_timer(h, period_usec);
 }
 
+/*
+  stop the SPI peripheral and set the SCK line as a GPIO to prevent the clock
+  line floating while we are waiting for the next spiStart()
+ */
+void SPIBus::stop_peripheral(void)
+{
+    if (!spi_started) {
+        return;
+    }
+    const auto &sbus = spi_devices[bus];
+#if HAL_SPI_SCK_SAVE_RESTORE
+    if (spi_mode == SPIDEV_MODE0 || spi_mode == SPIDEV_MODE1) {
+        // Clock polarity is 0, so we need to set the clock line low before spi reset
+        palClearLine(sbus.sck_line);
+    } else {
+        // Clock polarity is 1, so we need to set the clock line high before spi reset
+        palSetLine(sbus.sck_line);
+    }
+    palSetLineMode(sbus.sck_line, PAL_MODE_OUTPUT_PUSHPULL);
+#endif
+    spiStop(sbus.driver);
+    spi_started = false;
+}
+
+/*
+  start the SPI peripheral and restore the IO mode of the SCK line
+ */
+void SPIBus::start_peripheral(void)
+{
+    if (spi_started) {
+        return;
+    }
+
+    /* start driver and setup transfer parameters */
+    spiStart(spi_devices[bus].driver, &spicfg);
+#if HAL_SPI_SCK_SAVE_RESTORE
+    // restore sck pin mode from stop_peripheral()
+    palSetLineMode(spi_devices[bus].sck_line, sck_mode);
+#endif
+    spi_started = true;
+}
+
 /*
  used to acquire bus and (optionally) assert cs
 */
@@ -380,12 +424,9 @@ bool SPIDevice::acquire_bus(bool set, bool skip_cs)
         bus.spicfg.cr1 = (uint16_t)(freq_flag | device_desc.mode);
         bus.spicfg.cr2 = 0;
 #endif
-        if (bus.spi_started) {
-            spiStop(spi_devices[device_desc.bus].driver);
-            bus.spi_started = false;
-        }
-        spiStart(spi_devices[device_desc.bus].driver, &bus.spicfg);        /* Setup transfer parameters.       */
-        bus.spi_started = true;
+        bus.spi_mode = device_desc.mode;
+        bus.stop_peripheral();
+        bus.start_peripheral();
         if(!skip_cs) {
             spiSelectI(spi_devices[device_desc.bus].driver);                /* Slave Select assertion.          */
         }

libraries/AP_HAL_ChibiOS/SPIDevice.h

@@ -25,6 +25,10 @@
 #include "Scheduler.h"
 #include "Device.h"
 
+#ifndef HAL_SPI_SCK_SAVE_RESTORE
+#define HAL_SPI_SCK_SAVE_RESTORE FALSE
+#endif
+
 namespace ChibiOS {
 
 class SPIBus : public DeviceBus {
@@ -35,14 +39,28 @@ class SPIBus : public DeviceBus {
     SPIConfig spicfg;
     void dma_allocate(Shared_DMA *ctx);
     void dma_deallocate(Shared_DMA *ctx);
-    bool spi_started;
     uint8_t slowdown;
 
     // we need an additional lock in the dma_allocate and
     // dma_deallocate functions to cope with 3-way contention as we
     // have two DMA channels that we are handling with the shared_dma
     // code
     mutex_t dma_lock;
+
+    // store the last spi mode for stop_peripheral()
+    uint32_t spi_mode;
+
+    // start and stop the hardware peripheral
+    void start_peripheral(void);
+    void stop_peripheral(void);
+
+private:
+    bool spi_started;
+
+    // mode line for SCK pin
+#if HAL_SPI_SCK_SAVE_RESTORE
+    iomode_t sck_mode;
+#endif
 };
 
 struct SPIDesc {

libraries/AP_HAL_ChibiOS/hwdef/CubeOrangePlus/hwdef.dat

@@ -48,9 +48,9 @@ SPIDEV icm42688_ext   SPI4 DEVID4  ACCEL_EXT_CS  MODE3  2*MHZ  8*MHZ
 SPIDEV icm42688_ext2  SPI4 DEVID5  GYRO_EXT_CS   MODE3  2*MHZ  8*MHZ
 
 #IMU 2
-SPIDEV icm45686       SPI1 DEVID4  ICM45686_CS   MODE1  2*MHZ  8*MHZ
+SPIDEV icm45686       SPI1 DEVID4  ICM45686_CS   MODE0  2*MHZ  8*MHZ
 SPIDEV icm20649       SPI1 DEVID4  MPU_CS        MODE3  4*MHZ  8*MHZ
-SPIDEV icm45686_aux   SPI1 DEVID4  ICM45686_CS   MODE1  2*MHZ  8*MHZ
+SPIDEV icm45686_aux   SPI1 DEVID4  ICM45686_CS   MODE0  2*MHZ  8*MHZ
 SPIDEV icm20948_aux   SPI4 DEVID1  MPU_EXT_CS    MODE3  4*MHZ  8*MHZ
 
 # INSTANCE:<num> keyword is used to denote the instance number of the sensor
@@ -95,3 +95,5 @@ CHECK_IMU1_PRESENT      $CHECK_ICM20948_EXT || $CHECK_ICM42688_EXT2 || $CHECK_IC
 CHECK_IMU2_PRESENT      $CHECK_ICM42688_EXT || $CHECK_ICM45686_EXT
 
 BOARD_VALIDATE $CHECK_IMU0_PRESENT $CHECK_IMU1_PRESENT $CHECK_IMU2_PRESENT $CHECK_BARO0_PRESENT $CHECK_BARO1_PRESENT
+
+define HAL_SPI_SCK_SAVE_RESTORE TRUE

libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py

@@ -1417,9 +1417,11 @@ def write_SPI_config(f):
     for dev in spi_list:
         n = int(dev[3:])
         devlist.append('HAL_SPI%u_CONFIG' % n)
+        sck_pin = bylabel['SPI%s_SCK' % n]
+        sck_line = 'PAL_LINE(GPIO%s,%uU)' % (sck_pin.port, sck_pin.pin)
         f.write(
-            '#define HAL_SPI%u_CONFIG { &SPID%u, %u, STM32_SPI_SPI%u_DMA_STREAMS }\n'
-            % (n, n, n, n))
+            '#define HAL_SPI%u_CONFIG { &SPID%u, %u, STM32_SPI_SPI%u_DMA_STREAMS, %s }\n'
+            % (n, n, n, n, sck_line))
     f.write('#define HAL_SPI_BUS_LIST %s\n\n' % ','.join(devlist))
     write_SPI_table(f)