AM335x deassert periodic interrupt from rtc

Ali Utku Selen

How do you deassert periodic interrupt from RTC?

RTC_STATUS_REG (20.3.5.15) from AM335X TRM mentions you can clear interrupts for alarms but it doesn't say anything about how you should handle periodic interrupt.

What happens for me is, I have an interrupt handler for periodic interrupt which should be triggered every second and it does get that trigger however every second interrupt handler gets called more than once. I believe interrupt is active for sometime because number of calls to handler per trigger depends on how much I do in the handler.

Am I missing something from documentation?

over 11 years ago

0 Biser Gatchev-XID over 11 years ago

TI__Guru**** 393215 points

Hi,

I think the key sentence here is "The timer interrupt is a negative edge sensitive low-level pulse (1 OCP cycle duration)". The OCP clock is typically 100MHz, meaning that the timer interrupt stays active for 10ns.

0 Ali Utku Selen over 11 years ago in reply to Biser Gatchev-XID

Prodigy 40 points

Thanks for the answer. Do you have any idea what would be the efficient way to handle this scenario?

0 Biser Gatchev-XID over 11 years ago in reply to Ali Utku Selen

TI__Guru**** 393215 points

What software are you using? Can you check what the RTC OCP clock is set to?

0 Ali Utku Selen over 11 years ago in reply to Biser Gatchev-XID

Prodigy 40 points

Software is my own bare metal trials, I take after where ROM code leaves and just enable RTC clocks. I don't set anything else. So clocks should be default ones.

0 Biser Gatchev-XID over 11 years ago in reply to Ali Utku Selen

TI__Guru**** 393215 points

Yes, that would be 100MHz RTC OCP clock. MPU clock should be 500MHz in this case. I'm sorry, but I can't help with bare metal applications, there are simply too many things that have to be set up on this SoC.

0 Biser Gatchev-XID over 11 years ago in reply to Biser Gatchev-XID

TI__Guru**** 393215 points

Why don't you try AM335X Starterware. It has APIs for RTC usage.

0 Ali Utku Selen over 11 years ago in reply to Biser Gatchev-XID

Prodigy 40 points

I understand, thanks for the great help anyway.

I've checked RTC usage in Starterware but I couldn't see how they are avoiding my question.

examples/beaglebone/rtc/rtcClock.c -> RTCIsr().

That function prints stuff over uart which should make it enough to avoid getting interrupted by RTC again.

0 Harsha Kiran over 10 years ago

Intellectual 545 points

Hi Ali,

We had the same problem. It happens only when you operate at 600,720,1000 Mhz. At 300 MHz there are no spurrious interrupts.

We have modified the rtc-omap.c rtc_irq(....) function to update the events only once in a second.

Thanks,

Harsha

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AM335x deassert periodic interrupt from rtc