sama5d2x,cortex-A5, How do I set the priority of tick interrupts?

1,The priority of tick is set to 0, which is the lowest priority of hardware. It will crash after running for a while. xTickCount is no longer increased.
2,If the priority of the tick is set to 7 and the highest priority of the hardware, it is normal and will not crash.

(a)Can the tick priority of FreeRTOS system be set to the highest priority? I think it’s suggested to set it as the lowest priority.
(b)If it is set to the highest priority, what will be the problem?

Is this a documentation error? On the Cortex, 0 is always highest. This is documented in many places.

I saw it from ATMEL’s 2021 official datasheet.

Then, I looked up the documentation of sama5d3x, which is also the kernel of cortex-a5.
Also, 7 is the highest priority. Please see the figure below:

Will ATMEL(MICROCHIP) make such a huge mistake?

ok, sorry, I was referring to the Cortex M (your initial mention of the A escaped me, sorry):

Cutting Through the Confusion with Cortex-M Interrupt Priorities - Embedded blog - System - Arm Community

So what port are you using? Can you show us your freertosconfig.h?

It’s all right. Thank you for your reply.

FreeRTOSConfig.h,As follows:
(Refer to the official demo of FreeRTOS: CORTEX_A5_SAMA5D2x_Xplained_IAR)




 * Application specific definitions.


 * These definitions should be adjusted for your particular hardware and

 * application requirements.





 * See


#define configCPU_CLOCK_HZ                      /* Not used in this port as the value comes from the Atmel libraries. */


#define configUSE_TICKLESS_IDLE                 0

#define configTICK_RATE_HZ                      ( ( TickType_t ) 1000 )  

#define configUSE_PREEMPTION                    1

#define configUSE_IDLE_HOOK                     1

#define configUSE_TICK_HOOK                     1

#define configMAX_PRIORITIES                    ( 32 )

#define configMINIMAL_STACK_SIZE                ( ( unsigned short ) 100 )

#define configTOTAL_HEAP_SIZE                   ( ( size_t ) ( 32*1024 * 1024 ) )

#define configMAX_TASK_NAME_LEN                 ( 32 )

#define configUSE_TRACE_FACILITY                1

#define configUSE_16_BIT_TICKS                  0

#define configIDLE_SHOULD_YIELD                 0

#define configUSE_MUTEXES                       1

#define configQUEUE_REGISTRY_SIZE               32 // 8

#define configCHECK_FOR_STACK_OVERFLOW          0

#define configUSE_RECURSIVE_MUTEXES             1

#define configUSE_MALLOC_FAILED_HOOK            1

#define configUSE_APPLICATION_TASK_TAG          0

#define configUSE_COUNTING_SEMAPHORES           1

#define configUSE_TASK_NOTIFICATIONS            1

/* Co-routine definitions. */

#define configUSE_CO_ROUTINES                   0

#define configMAX_CO_ROUTINE_PRIORITIES         ( 2 )

/* Software timer definitions. */

#define configUSE_TIMERS                        1

#define configTIMER_TASK_PRIORITY               ( configMAX_PRIORITIES - 1 )

#define configTIMER_QUEUE_LENGTH                5

#define configTIMER_TASK_STACK_DEPTH            ( configMINIMAL_STACK_SIZE * 2 )

/* Set the following definitions to 1 to include the API function, or zero

to exclude the API function. */

#define INCLUDE_vTaskPrioritySet                1

#define INCLUDE_uxTaskPriorityGet               1

#define INCLUDE_vTaskDelete                     1

#define INCLUDE_vTaskCleanUpResources           1

#define INCLUDE_vTaskSuspend                    1

#define INCLUDE_vTaskDelayUntil                 1

#define INCLUDE_vTaskDelay                      1

#define INCLUDE_eTaskGetState                   1

#define INCLUDE_xEventGroupSetBitsFromISR       1

#define INCLUDE_xTimerPendFunctionCall          1

/* This demo makes use of one or more example stats formatting functions.  These

format the raw data provided by the uxTaskGetSystemState() function in to human

readable ASCII form.  See the notes in the implementation of vTaskList() within

FreeRTOS/Source/tasks.c for limitations. */


#define configFPU_D32   0

/* Prevent C code being included in assembly files when the IAR compiler is

used. */

#ifndef __IASMARM__

    /* The interrupt nesting test creates a 20KHz timer.  For convenience the

    20KHz timer is also used to generate the run time stats time base, removing

    the need to use a separate timer for that purpose.  The 20KHz timer

    increments ulHighFrequencyTimerCounts, which is used as the time base.

    Therefore the following macro is not implemented. */

    #define configGENERATE_RUN_TIME_STATS   0

    extern volatile uint32_t ulHighFrequencyTimerCounts;


    #define portGET_RUN_TIME_COUNTER_VALUE() ulHighFrequencyTimerCounts

    /* The size of the global output buffer that is available for use when there

    are multiple command interpreters running at once (for example, one on a UART

    and one on TCP/IP).  This is done to prevent an output buffer being defined by

    each implementation - which would waste RAM.  In this case, there is only one

    command interpreter running. */

    #define configCOMMAND_INT_MAX_OUTPUT_SIZE 3000

    /* Normal assert() semantics without relying on the provision of an assert.h

    header file. */

    void vAssertCalled( const char * pcFile, unsigned long ulLine );

    #define configASSERT( x ) if( ( x ) == 0 ) vAssertCalled( __FILE__, __LINE__ );

    /****** Hardware specific settings. *******************************************/


     * The application must provide a function that configures a peripheral to

     * create the FreeRTOS tick interrupt, then define configSETUP_TICK_INTERRUPT()

     * in FreeRTOSConfig.h to call the function.  FreeRTOS_Tick_Handler() must

     * be installed as the peripheral's interrupt handler.


    void vConfigureTickInterrupt( void );

    #define configSETUP_TICK_INTERRUPT() vConfigureTickInterrupt()


#endif /* __IASMARM__ */

#endif /* FREERTOS_CONFIG_H */

I couldn’t find the priority of your service ISR in that file. What is it set to? The service ISR must positively have the lowest of all configured interrupt priorities.

That chip has a proprietary interrupt controller, so the following page is relevant: and this file provides examples of installing interrupts

okay, thank you.
But after running for a while(Sometimes 3 minutes, sometimes 20 minutes, etc.),
xTickCount is no longer increased. What might be the reason?

Does the rest of the system (eg other ISRs and/or application tasks) still work, or is your system stuck in the infinite loop of a fault handler?

None of them work.
I debug with IAR and find that the MCU stops at this while sentence.

	/* uxDeletedTasksWaitingCleanUp is used to prevent vTaskSuspendAll()
	being called too often in the idle task. */
	while( uxDeletedTasksWaitingCleanUp > ( UBaseType_t ) 0U )
			pxTCB = ( TCB_t * ) listGET_OWNER_OF_HEAD_ENTRY( ( &xTasksWaitingTermination ) );
			( void ) uxListRemove( &( pxTCB->xStateListItem ) );

		prvDeleteTCB( pxTCB );

But I use IAR to check the variable value of uxDeletedTasksWaitingCleanUp , which is really 0.
That’s strange!

This code runs in the idle task and is what you would expect the code to be running if there are no application tasks that are able to run. IAR has a fully thread aware FreeRTOS plug-in that will show you what your other tasks are doing (they will be blocked on something if the Idle task is running).

The problem I encountered is a bit like this, but I can’t find the root cause.

The content of this post is also somewhat related to the problems I encountered. I’m studying it.
The version I use is FreeRTOS Kernel V10.0.0.

The Cortex-M devices have a different interrupt controller to your device.

Yes, Richard.

For the A5 chip I use, (interrupt priority 0-7)
If the priority of the tick is set to 0,
Can’t the API of a be called in interrupts with priority of 1-7?

The example code linked to previously would seem to indicate so. Assuming 0 is the lowest priority (it is a proprietary interrupt controller) it sets the priority of an interrupt that nests to 1 and one that doesn’t nest to 5. Check it’s FreeRTOS config file to see the max syscall priority, which presumably is less than 5 - can’t check myself as in my cell phone.

After further debugging, it is found that:

Debug serial port print information:

The program is dead here:

/* The high frequency interrupt given the highest priority or all. The priority

of the lower frequency timers must still be above the tick interrupt priority. */

#define tmrLOWER_PRIORITY 1

#define tmrHIGHER_PRIORITY 5

You mean the priority setting here? in the “IntQueueTimer.h”.

Hi, Richard.
Is there an error in the comments here?
Should TC2 be changed to TC1?

Did you check the source ? Should be easy to verify.