Implementation for can_read to be deferred to thread context when rx

interrupt is enabled.

Author: MubeenHCLite

targets/TARGET_STM/can_api.c

@@ -646,8 +646,12 @@ void can_irq_set(can_t *obj, CanIrqType type, uint32_t enable)
 #include <string.h>
 #include <inttypes.h>
 
+#define ENABLED true
+#define DISABLED false
+
 static uint32_t can_irq_ids[CAN_NUM] = {0};
 static can_irq_handler irq_handler;
+static uint32_t rx_irq_status = DISABLED;
 
 static void can_registers_init(can_t *obj)
 {
@@ -767,6 +771,7 @@ void can_irq_free(can_t *obj)
     can->IER &= ~(CAN_IT_FMP0 | CAN_IT_FMP1 | CAN_IT_TME | \
                   CAN_IT_ERR | CAN_IT_EPV | CAN_IT_BOF);
     can_irq_ids[obj->index] = 0;
+    rx_irq_status = DISABLED;
 }
 
 void can_free(can_t *obj)
@@ -998,6 +1003,10 @@ int can_read(can_t *obj, CAN_Message *msg, int handle)
         can->RF1R |= CAN_RF1R_RFOM1;
     }
 
+    if(rx_irq_status == ENABLED) {
+        __HAL_CAN_ENABLE_IT(&obj->CanHandle, CAN_IT_FMP0);
+    }
+
     return 1;
 }
 
@@ -1011,6 +1020,7 @@ void can_reset(can_t *obj)
 
     /* restore registers state as saved in obj context */
     can_registers_init(obj);
+    rx_irq_status = DISABLED;
 }
 
 unsigned char can_rderror(can_t *obj)
@@ -1162,6 +1172,11 @@ static void can_irq(CANName name, int id)
     tmp1 = __HAL_CAN_MSG_PENDING(&CanHandle, CAN_FIFO0);
     tmp2 = __HAL_CAN_GET_IT_SOURCE(&CanHandle, CAN_IT_FMP0);
 
+    // In legacy can, reading is the only way to clear rx interrupt. But can_read has mutex locks
+    // since mutexes cannot be used in ISR context, rx interrupt is masked here to temporary disable it
+    // rx interrupts will be unamsked in read operation. reads must be deffered to thread context.
+    __HAL_CAN_DISABLE_IT(&CanHandle, CAN_IT_FMP0);
+
     if ((tmp1 != 0) && tmp2) {
         irq_handler(can_irq_ids[id], IRQ_RX);
     }
@@ -1261,6 +1276,7 @@ void can_irq_set(can_t *obj, CanIrqType type, uint32_t enable)
                 ier = CAN_IT_FMP0;
                 irq_n = CAN1_IRQ_RX_IRQN;
                 vector = (uint32_t)&CAN1_IRQ_RX_VECT;
+                rx_irq_status = ENABLED;
                 break;
             case IRQ_TX:
                 ier = CAN_IT_TME;
@@ -1293,6 +1309,7 @@ void can_irq_set(can_t *obj, CanIrqType type, uint32_t enable)
                 ier = CAN_IT_FMP0;
                 irq_n = CAN2_IRQ_RX_IRQN;
                 vector = (uint32_t)&CAN2_IRQ_RX_VECT;
+                rx_irq_status = ENABLED;
                 break;
             case IRQ_TX:
                 ier = CAN_IT_TME;
@@ -1326,6 +1343,7 @@ void can_irq_set(can_t *obj, CanIrqType type, uint32_t enable)
                 ier = CAN_IT_FMP0;
                 irq_n = CAN3_IRQ_RX_IRQN;
                 vector = (uint32_t)&CAN3_IRQ_RX_VECT;
+                rx_irq_status = ENABLED;
                 break;
             case IRQ_TX:
                 ier = CAN_IT_TME;