AP_HAL_ChibiOS: add support for saving and restoring SCK pin state

when SPI goes into undefined state during reset

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 +87,8 @@ 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()
+    sck_mode = palReadLineMode(spi_devices[bus].sck_line);
 }
 
 /*
@@ -103,10 +106,7 @@ 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 +339,46 @@ 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 (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);
+    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);
+
+    // restore sck pin mode from stop_peripheral()
+    palSetLineMode(spi_devices[bus].sck_line, sck_mode);
+
+    spi_started = true;
+}
+
 /*
  used to acquire bus and (optionally) assert cs
 */
@@ -380,12 +420,9 @@ 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

@@ -35,7 +35,6 @@ public:
     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
@@ -43,6 +42,19 @@ public:
     // 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
+    iomode_t sck_mode;
 };
 
 struct SPIDesc {

libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py

@@ -1403,26 +1403,26 @@ def write_SPI_table(f):
     f.write("\n")
 
 
-def write_SPI_config(f):
+def write_SPI_config(self, f):
     '''write SPI config defines'''
-    global spi_list
-    for t in list(bytype.keys()) + list(alttype.keys()):
+    for t in list(self.bytype.keys()) + list(self.alttype.keys()):
         if t.startswith('SPI'):
-            spi_list.append(t)
-    spi_list = sorted(spi_list)
-    if len(spi_list) == 0:
+            self.spi_list.append(t)
+    self.spi_list = sorted(self.spi_list)
+    if len(self.spi_list) == 0:
         f.write('#define HAL_USE_SPI FALSE\n')
         return
     devlist = []
-    for dev in spi_list:
+    for dev in self.spi_list:
         n = int(dev[3:])
         devlist.append('HAL_SPI%u_CONFIG' % n)
+        sck_pin = self.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)
-
+    self.write_SPI_table(f)
 
 def write_QSPI_table(f):
     '''write SPI device table'''