CCS/PROCESSOR-SDK-AM437X: Building Starterware projects

Hi Pavel,

Thank for your pointers. Sorry for the delay in replying.The DMtimer-3 issue is now resolved after I referred to the pdk_am437x/packages/ti/drv/usb/example/common/timer.c file.

Here's the solution for reference. I added the following to my code:

#define CM_PER_TIMER3_CLKCTRL (0x44DF8800 + 0x538) // PRCM_CM_PER_TIMER3_CLKCTRL
#define CM_DPLL_CLKSEL_TIMER3_CLK (0x44DF4200 + 0x8)

// clock source to CLK_M_OSC: 0x1 - high frequency input clock (24MHz)
// CLK_32KHz: 0x2
// TCLKIN : 0x0 - external clock pin - not used.

*(unsigned int*)CM_DPLL_CLKSEL_TIMER3_CLK = 0x1;

// enable the TIMER
*(unsigned int*)CM_PER_TIMER3_CLKCTRL = 0x2;

I have a follow-up question. I am trying to benchmark the interrupt latency using DMTimer3 on this processor but the latency seems to be too high - around 40usec.

Here's the relevant snippet:

Void myIsr(UArg arg0)
{

time2 = Timestamp_get32();

Semaphore_post(semaphore0);

}

//inside the TASK :-

Timestamp_getFreq(&freq);
BIOS_getCpuFreq(&freq2);
System_printf("\nTimeStamp Frequency = %lu Hz!\n", freq.lo ); //This comes out to be 1GHZ = 1ns resolution
System_printf("\nBIOS Frequency = %lu Hz!\n", freq2.lo ); //This comes out to be 1GHZ = 1ns resolution

Timer_Params_init(&timerParams);

timerParams.period = 100; //100usec timer
timerParams.runMode = Timer_RunMode_ONESHOT;
timerParams.periodType = Timer_PeriodType_MICROSECS;
timerParams.startMode = Timer_StartMode_USER; //User starts the timer

myTimer = Timer_create(3, (TimerP_Fxn) myIsr, &timerParams, &eb); //Timer_ANY
if (myTimer == NULL) {
System_abort("Timer create failed");
}

Timer_setPeriodMicroSecs(myTimer, (uint32_t)100); //Double check the period

Timer_getFreq(myTimer, &freq);
System_printf("\nTimer Frequency = %lu Hz!\n", freq.lo ); // Comes out to be 24 MHz

System_printf("\nTimer Period = %lu ns!\n", ( Timer_getPeriod(myTimer)*40) ); //*40ns @ 24MHz DMtimer freq; --> Comes out to be ~100usec

for(i = 0; i < 100000; i++){

time1 = Timestamp_get32();
Timer_start(myTimer);
Semaphore_pend(semaphore0, BIOS_WAIT_FOREVER); //Wait for the DMTimer3 ISR to "Post" the semaphore
time2 = Timestamp_get32();

delta = time2 - (time1+100000); //add t1+100,000nsec = expected time the DmTimer3 should ideally fire
if(delta < min_delta){
min_delta = delta;
}
else if(delta > max_delta){
max_delta = delta;
}

}

System_printf("Timer_start min_delta = %ld \n", min);
System_printf("Timer_start max_delta = %ld \n", max);

Could you help me find the cause that is introducing such high latencies?

Thanks,

Virendra 

Hello Pavel,

Looks like there is a negative 40 usec latency, meaning the timer fires 40 usec earlier than required instead of the earlier mentioned positive latency.

Please could you have a look at the above code and let me know why this might be happening? A timer parameter, timerParams.period = 100 & timerParams.periodType = Timer_PeriodType_MICROSECS, should in-fact correspond to 100 usec.  

Thanks,

Virendra

Virendra,

Virendra Kate said:

Looks like there is a negative 40 usec latency, meaning the timer fires 40 usec earlier than required instead of the earlier mentioned positive latency.

Please could you have a look at the above code and let me know why this might be happening? A timer parameter, timerParams.period = 100 & timerParams.periodType = Timer_PeriodType_MICROSECS, should in-fact correspond to 100 usec.  

I would suggest you to dump DMTIMER3 registers values and check if these correspond to 100us resolution.

You can also explore the timer diagnostic test. The Timer is configured for 1msec interrupt.

pdk_am437x_x/packages/ti/board/diag/timer/

Regarding timer resolution hints, you can also refer the below e2e threads:

Regards,
Pavel