RE: [ECOS] Problem with spurious interrupt on ARM

[Morten Laursen <MLA at rtx dot dk>]

If it's supposed to work like this, then I don't understand the purpose of
HAL option "Ignore spurious (fleeting) interrupts".

Anyway, it's a viable solution. Thanks.

Venlig Hilsen / Regards 
Morten

-- 
Morten Laursen, M.Sc.S.E.
RTX Telecom A/S - http://www.rtx.dk/
Direct phone: (+45) 96 32 24 03


> -----Original Message-----
> From: Andrew Lunn [mailto:andrew.lunn@ascom.ch]
> Sent: 30. august 2002 12:34
> To: Morten Laursen
> Cc: 'ecos-discuss@sources.redhat.com'
> Subject: Re: [ECOS] Problem with spurious interrupt on ARM
> 
> 
> On Fri, Aug 30, 2002 at 12:11:54PM +0200, Morten Laursen wrote:
> > According to the MCU (AT91M40800) data sheet a spurious 
> interrupt can happen
> > when using edge trigged interupts. I use edge trigged 
> interrupts, because I
> > want to know how long time the button was pressed.
> > 
> > So (as I understand it) the problem is not, that there is a spurious
> > interrupt, but that it is somehow handled incorrectly?
> 
> I think its actually a design philosophy thing. Hardware should not
> produce spurious interrupts. If it does, its broken. So eCos general
> does not have to deal with spurious interrupts. If your broken
> hardware does generate such things, you have to work around your
> broken hardware. In this case, you need to modify either your
> application or the HAL for the AT91M40800 to deal with this.
> 
> int hal_IRQ_handler(void)
> {
>     cyg_uint32 irq_num;
>     cyg_uint32 ipr, imr;
> 
>     HAL_READ_UINT32(AT91_AIC+AT91_AIC_IPR, ipr);
>     HAL_READ_UINT32(AT91_AIC+AT91_AIC_IMR, imr);
>     ipr &= imr;
>     for (irq_num = 0;  irq_num < 19;  irq_num++) {
>         if (ipr & (1 << irq_num)) {
>             break;
>         }
>     }
> 
>     return irq_num;
> }
> 
> So this will drop out with 19 in the case of a spurious interrupt.
> 
> So put a handler on interrupt 19 which clears the interrupt.
> 
>    Andrew
> 
> 

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