[SOLVED] Timeline not showing SysTick or Scheduler events

piconomix · Sep 22nd 2020, 10:25am

Hi there!

I'm trying to get Segger SysView working with FreeRTOS v10.3.1 on an ARM Cortex M0+. I applied the FreeRTOSV10_Core.patch by hand, added the example SEGGER_SYSVIEW_X_GetTimestamp() function and increment the SEGGER_SYSVIEW_TickCnt variable at the start of xPortSysTickHandler() in FreeRTOS/Source/portable/GCC/ARM_CM0/port.c as follows:

C Source Code

#ifdef CFG_SEGGER_SYSVIEW_ENABLED
volatile uint32_t SEGGER_SYSVIEW_TickCnt;
#endif
void xPortSysTickHandler( void )
{
uint32_t ulPreviousMask;
#ifdef CFG_SEGGER_SYSVIEW_ENABLED
SEGGER_SYSVIEW_TickCnt++;
#endif
ulPreviousMask = portSET_INTERRUPT_MASK_FROM_ISR();
traceISR_ENTER();
{
/* Increment the RTOS tick. */
if( xTaskIncrementTick() != pdFALSE )
{
traceISR_EXIT_TO_SCHEDULER();
/* Pend a context switch. */
portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
}
else
{
traceISR_EXIT();
}
}
portCLEAR_INTERRUPT_MASK_FROM_ISR( ulPreviousMask );
}

Display All

The SysTick and Scheduler events are shown correctly with timestamps in the event log but they are not displayed in the Timeline window:

I also noticed that there is a "No runtime!" warning.

Attached is "freertos_v10_3_1.SVDat" for inspection. It looks like my patch to FreeRTOS V10.3.1 was not completely successful. Any hints / tips on how to fix it would be much appreciated!

Thanks in advance,
Pieter
piconomix.com

piconomix · Sep 27th 2020, 1:01pm

Hi everyone,

I've identified and fixed the problem

The Segger Systemview GUI is not able to cope with events that are not timestamped properly (sequentially).

For the Cortex M0/M0+ the usual time stamping mechanism is to use SysTick (system timer). The problem is that FreeRTOS only configures and enables SysTick when vTaskStartScheduler() is called, so all Segger SysView events that happen before this are timestamped with the same zero value (0).

This leads to a catch 22 situation, because I want to see events that lead up to starting the scheduler, but the events can not be timestamped properly without starting the scheduler.

My solution was to ditch SysTick for time stamping and use TIM7 as a dedicated 1 us time stamping counter on the STM32. I can configure and start TIM7 before calling SEGGER_SYSVIEW_Init(). See here for my implementation:

github.com/piconomix/piconomix…SYSVIEW_Config_FreeRTOS.c

Feedback for the Segger R&D team: I noticed this comment in the documentation, but the implication should really be explained better:

In case timestamp is not retrieved from cycle counter but from system timer, SEGGER_SYSVIEW_TickCnt must be incremented in the SysTick handler before any SYSVIEW event is generated.

I guess what you mean to say is that the SysTick timestamping handler must be configured and running before generating any SYSVIEW events.

Kind regards,
Pieter
piconomix.com

SEGGER - Nino · Sep 29th 2020, 1:04pm

Hello Pieter,

Thank you for your inquiry.

piconomix wrote:

Feedback for the Segger R&D team: I noticed this comment in the documentation, but the implication should really be explained better:

In case timestamp is not retrieved from cycle counter but from system timer, SEGGER_SYSVIEW_TickCnt must be incremented in the SysTick handler before any SYSVIEW event is generated.

I guess what you mean to say is that the SysTick timestamping handler must be configured and running before generating any SYSVIEW events.

Correct. The documentation implies this with its wording, but we will review how the documentation can be improved in this regards.

Best regards,
Nino

C Source Code

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