fix: the HSI48 oscillator is disabled by the random number generator (#606)

Author: brianvanderbeek-philips

hal_st/synchronous_stm32fxxx/SynchronousHardwareSemaphoreStm.cpp

@@ -17,7 +17,7 @@ namespace hal
     {
         HSEM->C1IER |= 1 << static_cast<uint32_t>(semaphore);
 
-        while (HSEM->RLR[static_cast<uint32_t>(semaphore)] != (HSEM_R_LOCK | HSEM_CR_COREID_CURRENT))
+        while (!IsLockedByCurrentCore(semaphore))
         {}
     }
 
@@ -29,6 +29,11 @@ namespace hal
         HSEM->C1IER &= ~mask;
     }
 
+    bool SynchronousHardwareSemaphoreMasterStm::IsLockedByCurrentCore(hal::Semaphore semaphore) const
+    {
+        return HSEM->RLR[static_cast<uint32_t>(semaphore)] == HSEM_R_LOCK | HSEM_CR_COREID_CURRENT;
+    }
+
     SynchronousHardwareSemaphoreStm::SynchronousHardwareSemaphoreStm(SynchronousHardwareSemaphoreMasterStm& synchronousHardwareSemaphoreMaster, Semaphore semaphore)
         : synchronousHardwareSemaphoreMaster(synchronousHardwareSemaphoreMaster)
         , semaphore(semaphore)

hal_st/synchronous_stm32fxxx/SynchronousHardwareSemaphoreStm.hpp

@@ -27,6 +27,7 @@ namespace hal
 
         void WaitLock(hal::Semaphore semaphore) const;
         void Release(hal::Semaphore semaphore) const;
+        bool IsLockedByCurrentCore(hal::Semaphore semaphore) const;
     };
 
     class SynchronousHardwareSemaphoreStm

hal_st/synchronous_stm32fxxx/SynchronousSynchronizedRandomDataGeneratorStm.cpp

@@ -1,4 +1,5 @@
 #include "hal_st/synchronous_stm32fxxx/SynchronousSynchronizedRandomDataGeneratorStm.hpp"
+#include "infra/util/ReallyAssert.hpp"
 #include "stm32wbxx.h"
 
 namespace hal
@@ -11,15 +12,35 @@ namespace hal
     void SynchronousSynchronizedRandomDataGeneratorStm::GenerateRandomData(infra::ByteRange result)
     {
         auto semaphore = hal::SynchronousHardwareSemaphoreStm(synchronousHardwareSemaphoreMasterStm, hal::Semaphore::randomNumberGenerator);
-
-        LL_RCC_HSI48_Enable();
-        while (!LL_RCC_HSI48_IsReady())
-        {}
+        Hsi48Enabler hsi48Enabler(synchronousHardwareSemaphoreMasterStm);
 
         hwRngCreator.Emplace();
         hwRngCreator->GenerateRandomData(result);
         hwRngCreator.Destroy();
+    }
+
+    SynchronousSynchronizedRandomDataGeneratorStm::Hsi48Enabler::Hsi48Enabler(hal::SynchronousHardwareSemaphoreMasterStm& synchronousHardwareSemaphoreMasterStm)
+    {
+        bool clockConfigurationLocked = synchronousHardwareSemaphoreMasterStm.IsLockedByCurrentCore(hal::Semaphore::recoveryAndIndependentClockConfiguration);
 
-        LL_RCC_HSI48_Disable();
+        if (clockConfigurationLocked)
+        {
+            // HSI48 should already be enabled when the clock configuration is locked. Don't manage its lifecycle.
+            really_assert(LL_RCC_HSI48_IsReady());
+        }
+        else
+        {
+            LL_RCC_HSI48_Enable();
+            while (!LL_RCC_HSI48_IsReady())
+            {}
+
+            disableHsi48OnFinalization = true;
+        }
+    }
+
+    SynchronousSynchronizedRandomDataGeneratorStm::Hsi48Enabler::~Hsi48Enabler()
+    {
+        if (disableHsi48OnFinalization)
+            LL_RCC_HSI48_Disable();
     }
 }

hal_st/synchronous_stm32fxxx/SynchronousSynchronizedRandomDataGeneratorStm.hpp

@@ -16,6 +16,16 @@ namespace hal
         void GenerateRandomData(infra::ByteRange result) override;
 
     private:
+        class Hsi48Enabler
+        {
+        public:
+            Hsi48Enabler(hal::SynchronousHardwareSemaphoreMasterStm& synchronousHardwareSemaphoreMasterStm);
+            ~Hsi48Enabler();
+
+        private:
+            bool disableHsi48OnFinalization = false;
+        };
+
         infra::DelayedProxyCreator<hal::SynchronousRandomDataGenerator, void()> hwRngCreator;
         hal::SynchronousHardwareSemaphoreMasterStm& synchronousHardwareSemaphoreMasterStm;
     };