STM32WB: Add TRNG HW Semaphore

Because TRNG is a shared resource between the 2 STM32WB cores, SW needs
to acquire HW Semaphore before using the resource.

Author: LMESTM

targets/TARGET_STM/trng_api.c

@@ -25,6 +25,11 @@
 #include "trng_api.h"
 #include "mbed_error.h"
 #include "mbed_critical.h"
+#if defined (TARGET_STM32WB)
+/*  Family specific include for WB with HW semaphores */
+#include "hw.h"
+#include "hw_conf.h"
+#endif
 
 static uint8_t users = 0;
 
@@ -63,18 +68,36 @@ void trng_init(trng_t *obj)
     obj->handle.State = HAL_RNG_STATE_RESET;
     obj->handle.Lock = HAL_UNLOCKED;
 
+#if defined(CFG_HW_RNG_SEMID)
+    /*  In case RNG is a shared ressource, get the HW semaphore first */
+    while( LL_HSEM_1StepLock( HSEM, CFG_HW_RNG_SEMID ) );
+#endif
     HAL_RNG_Init(&obj->handle);
 
     /* first random number generated after setting the RNGEN bit should not be used */
     HAL_RNG_GenerateRandomNumber(&obj->handle, &dummy);
+
+#if defined(CFG_HW_RNG_SEMID)
+    LL_HSEM_ReleaseLock( HSEM, CFG_HW_RNG_SEMID, 0 );
+#endif
 }
 
 void trng_free(trng_t *obj)
 {
+#if defined(CFG_HW_RNG_SEMID)
+    /*  In case RNG is a shared ressource, get the HW semaphore first */
+    while( LL_HSEM_1StepLock( HSEM, CFG_HW_RNG_SEMID ) );
+#endif
     /*Disable the RNG peripheral */
     HAL_RNG_DeInit(&obj->handle);
+
+#if defined(CFG_HW_RNG_SEMID)
+    /*  In case RNG is a shared ressource, get the HW semaphore first */
+    LL_HSEM_ReleaseLock( HSEM, CFG_HW_RNG_SEMID, 0 );
+#else
     /* RNG Peripheral clock disable - assume we're the only users of RNG  */
     __HAL_RCC_RNG_CLK_DISABLE();
+#endif
 
     users = 0;
 }
@@ -85,6 +108,11 @@ int trng_get_bytes(trng_t *obj, uint8_t *output, size_t length, size_t *output_l
     volatile uint8_t random[4];
     *output_length = 0;
 
+#if defined(CFG_HW_RNG_SEMID)
+    /*  In case RNG is a shared ressource, get the HW semaphore first */
+    while( LL_HSEM_1StepLock( HSEM, CFG_HW_RNG_SEMID ) );
+#endif
+
     /* Get Random byte */
     while ((*output_length < length) && (ret == 0)) {
         if (HAL_RNG_GenerateRandomNumber(&obj->handle, (uint32_t *)random) != HAL_OK) {
@@ -103,6 +131,11 @@ int trng_get_bytes(trng_t *obj, uint8_t *output, size_t length, size_t *output_l
         ret = -1;
     }
 
+#if defined(CFG_HW_RNG_SEMID)
+    /*  In case RNG is a shared ressource, get the HW semaphore first */
+    LL_HSEM_ReleaseLock( HSEM, CFG_HW_RNG_SEMID, 0 );
+#endif
+
     return (ret);
 }