Fixes to the device layer/nRF implementation

* Correctly dispatch at compile time on the NRF_SDH_DISPATCH_MODEL
  rather than on the enum that defines the model.  This change enables
  the softdevice to actually use the right queue posting primitives.

* When NRF_DEBUG is enabled, softdevice will dispatch log statements
  from interrupt context.  In order to support this, if appropriate,
  log timestamping needs to be available; in turn, this implies that
  TicksSinceBoot must be callable from interrupt context.  Since
  FreeRTOS does not provide generalized facility to determine whether
  a function is in an interrupt context, we make the symbol weak here,
  and leave it to more specific adaptations to provide a more robust
  implementation.

* With softdevice executing code in the interrupt context, pbuf_alloc
  in LwIP must also be callable from the interrupt context.  Following
  a survey of usage of SYS_ARCH_{PROTECT|UNPROTECT} in LwIP code, it
  is appropriate to use the task{ENTER|EXIT}_CRITICAL_FROM_ISR
  variants of the critical sections.

Author: robszewczyk

src/adaptations/device-layer/FreeRTOS/SystemTimeSupport.cpp

@@ -40,24 +40,64 @@ constexpr uint32_t kTicksOverflowShift = (configUSE_16_BIT_TICKS) ? 16 : 32;
 
 uint64_t sBootTimeUS = 0;
 
-uint64_t TicksSinceBoot(void)
+#ifdef __CORTEX_M
+BaseType_t sNumOfOverflows;
+#endif
+} // unnamed namespace
+
+/**
+ * Returns the number of FreeRTOS ticks since the system booted.
+ *
+ * NOTE: The default implementation of this function uses FreeRTOS's
+ * vTaskSetTimeOutState() function to get the total number of ticks,
+ * irrespective of tick counter overflows.  Unfortunately, this function cannot
+ * be called in interrupt context, no equivalent ISR function exists, and
+ * FreeRTOS provides no portable way of determining whether a function is being
+ * called in an interrupt context.  Adaptations that need to use the Weave
+ * Get/SetClock methods from within an interrupt handler must override this
+ * function with a suitable alternative that works on the target platform.  The
+ * provided version is safe to call on ARM Cortex platforms with CMSIS
+ * libraries.
+ */
+
+uint64_t FreeRTOSTicksSinceBoot(void) __attribute__((weak));
+
+uint64_t FreeRTOSTicksSinceBoot(void)
 {
     TimeOut_t timeOut;
+
+#ifdef __CORTEX_M
+    if (SCB->ICSR & SCB_ICSR_VECTACTIVE_Msk) // running in an interrupt context
+    {
+        // Note that sNumOverflows may be quite stale, and under those
+        // circumstances, the function may violate monotonicity guarantees
+        timeout.xTimeOnEntering = xTaskGetTickCountFromISR();
+        timeout.xOverflowCount = sNumOfOverflows;
+    }
+    else
+    {
+#endif
+
     vTaskSetTimeOutState(&timeOut);
+
+#ifdef __CORTEX_M
+    // BaseType_t is supposed to be atomic
+    sNumOfOverflows = timeOut.xOverflowCount;
+    }
+#endif
+
     return static_cast<uint64_t>(timeOut.xTimeOnEntering) +
           (static_cast<uint64_t>(timeOut.xOverflowCount) << kTicksOverflowShift);
 }
 
-} // unnamed namespace
-
 uint64_t GetClock_Monotonic(void)
 {
-    return (TicksSinceBoot() * kMicrosecondsPerSecond) / configTICK_RATE_HZ;
+    return (FreeRTOSTicksSinceBoot() * kMicrosecondsPerSecond) / configTICK_RATE_HZ;
 }
 
 uint64_t GetClock_MonotonicMS(void)
 {
-    return (TicksSinceBoot() * kMillisecondPerSecond) / configTICK_RATE_HZ;
+    return (FreeRTOSTicksSinceBoot() * kMillisecondPerSecond) / configTICK_RATE_HZ;
 }
 
 uint64_t GetClock_MonotonicHiRes(void)

src/adaptations/device-layer/nRF5/BLEManagerImpl.cpp

@@ -802,7 +802,7 @@ void BLEManagerImpl::SoftDeviceBLEEventCallback(const ble_evt_t * bleEvent, void
     }
 
     // Post the event to the Weave queue.
-#if NRF_SDH_DISPATCH_MODEL_INTERRUPT
+#if (NRF_SDH_DISPATCH_MODEL == NRF_SDH_DISPATCH_MODEL_INTERRUPT)
     BaseType_t yieldRequired;
     PlatformMgrImpl().PostEventFromISR(&event, yieldRequired);
     portYIELD_FROM_ISR(yieldRequired);
@@ -1050,4 +1050,3 @@ bool BLEManagerImpl::IsSubscribed(uint16_t conId)
 } // namespace nl
 
 #endif // WEAVE_DEVICE_CONFIG_ENABLE_WOBLE
-

src/lwip/freertos/arch/sys_arch.h

@@ -33,7 +33,7 @@ typedef QueueHandle_t sys_mbox_t;
 typedef xSemaphoreHandle sys_mutex_t;
 typedef xSemaphoreHandle sys_sem_t;
 typedef TaskHandle_t sys_thread_t;
-typedef int sys_prot_t;
+typedef UBaseType_t sys_prot_t;
 
 #include "arch/sys_arch.h"
 #include "lwip/opt.h"

src/lwip/freertos/sys_arch.c

@@ -274,12 +274,11 @@ u32_t sys_now(void)
 
 sys_prot_t sys_arch_protect(void)
 {
-    taskENTER_CRITICAL();
-    return 1;
+    return taskENTER_CRITICAL_FROM_ISR();
 }
 
 void sys_arch_unprotect(sys_prot_t pval)
 {
-    taskEXIT_CRITICAL();
+    taskEXIT_CRITICAL_FROM_ISR(pval);
 }