topic Re: EPIT Interrupt number in i.MX Processors

EPIT Interrupt number

matthiasalbrech — Thu, 04 Jan 2018 12:28:38 GMT

I need a periodic timer interrupt on i.mx6. For that I developed a LKM: The EPIT Timer counts and every second the output compare interrupt flag is set. But its not possible to make Interrupts hapen because I don't know the Interrupt number:

request_irq(88, &timer_interrupt, IRQF_TIMER| IRQF_IRQPOLL, "EPIT Interrupt", NULL);

doesn't work. the function "timer_interrupt" is called all the time, although I switch off the EPIT timer and clear the compare interrupt flag. It seems that 88 is just the hardware interrupt address and I have to type in something different instead. Where I can find the correct interrupt number for the irq?

thanks,

Matthias

Re: EPIT Interrupt number

fabio_estevam — Sat, 06 Jan 2018 22:55:28 GMT

What about using arch/arm/mach-imx/epit.c instead?

Regards,

Fabio Estevam

Re: EPIT Interrupt number

matthiasalbrech — Mon, 08 Jan 2018 07:57:34 GMT

Hi,

thanks for the hint.

epit.c is just a reference code and there are lot of undefined symbols ("#include <asm/mach/time.h>": Unresolved inklusion, "#include "common.h"": no such file ore directory, "#include "hardware.h": Unresolved inklusion, "CLOCK_EVT_MODE_UNUSED" could not be resolved, "CLOCK_EVT_MODE_PERIODIC" could not be resolved ...". So its not easy to test the code. But I think that the interrupt part is mostly the same:

static void epit_irq_acknowledge(void)
{
__raw_writel(EPITSR_OCIF, timer_base + EPITSR);
}

static irqreturn_t epit_timer_interrupt(int irq, void *dev_id)
{
struct clock_event_device *evt = &clockevent_epit;

epit_irq_acknowledge();

evt->event_handler(evt);

return IRQ_HANDLED;
}

static struct irqaction epit_timer_irq = {
   .name       = "i.MX EPIT Timer Tick",
   .flags       = IRQF_TIMER | IRQF_IRQPOLL,
   .handler   = timer_interrupt,
};

...

setup_irq(irq, &epit_timer_irq);

but I dont understand from where this code gets the irq number in "setup_irq(irq, &epit_timer_irq);".

In arch/arm/boot/dts/imx6qdl.dtsi I can see, that the number is 56. But if I use 56 as the interrupt number in my code instead of 88, the interrupt is never executed. Any idea?

Re: EPIT Interrupt number

fabio_estevam — Mon, 08 Jan 2018 13:28:04 GMT

Hi Matthias,

The reference manual states that 88 is the interrupt number for EPIT1.

In the dtsi the irq numbers have a 32 offset, so 88 - 32 = 56 is the number you will see in the dtsi.

You should be able to get the irq number by doing platform_get_irq()

By the way, why do you need EPIT1? Can't you just use GPT instead?

Regards,

Fabio Estevam

Re: EPIT Interrupt number

fabio_estevam — Mon, 08 Jan 2018 20:18:01 GMT

Actually you should use irq_of_parse_and_map() to retrieve the irq, just like it is done inside drivers/clocksource/timer-imx-gpt.c

Regards,

Fabio Estevam

Re: EPIT Interrupt number

matthiasalbrech — Tue, 09 Jan 2018 16:03:11 GMT

Hi,

thanks for the quick response.

I use EPIT because its actually not used. Would it be an advantage to use GPT?

I solved the problem with your help. Its not a smart solution because there are some warnings (initialisation makes integer from pointer without cast...), but it works:

int np = of_find_node_by_name(NULL,"epit");

int virq = irq_of_parse_and_map(np,0);

ret=request_irq(0x118, &timer_interrupt,__IRQF_TIMER | IRQF_IRQPOLL, "EPIT Interrupt", NULL);

thanks again for your help