Date: Wed, 26 Jul 2006 14:38:38 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-mobile@freebsd.org Cc: "Douglas W. Goodall" <douglas_goodall@mac.com> Subject: Re: Stray irq 7's Message-ID: <200607261438.39241.jhb@freebsd.org> In-Reply-To: <000901c6ae96$c03a2000$6dce46c0@dougwide> References: <000901c6ae96$c03a2000$6dce46c0@dougwide>
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On Sunday 23 July 2006 16:29, Douglas W. Goodall wrote:
> I am a very knowlegeable OS software engineer and I know the stray irq7
> problem intimately.
>
> The PIC (programable interrupt controller) used in PCs is sensitive and will
> raise an IR7 interrupt without a valid cause. This has been going on since
> S100 systems. We used to call it the vacuum cleaner interrupt because just
> about anything can cause it.
>
> The only fix for it is to enhance the source code of the interrupt routine
> to accept the interrupt and scrub the PIC.
>
> The problem is documented in the Intel publications. I have the same problem
> with my Sharp PC-MM20.
> You have two choices. See if you can ignore the problem, if it doesn't
> occur too often. Or encourage the FreeBSD
> Engineers to add the required code to the interrupt code. Or do it
> yourself. The PIC is complicated though and
> if you place it in the wrong mode, things will not work correctly.
Sadly the code already does the check (see src/sys/i386/isa/atpic.c):
/*
* If we don't have an event, see if this is a spurious
* interrupt.
*/
if (isrc->is_event == NULL &&
(iframe.if_vec == 7 || iframe.if_vec == 15)) {
int port, isr;
/*
* Read the ISR register to see if IRQ 7/15 is really
* pending. Reset read register back to IRR when done.
*/
port = ((struct atpic *)isrc->is_pic)->at_ioaddr;
mtx_lock_spin(&icu_lock);
outb(port, OCW3_SEL | OCW3_RR | OCW3_RIS);
isr = inb(port);
outb(port, OCW3_SEL | OCW3_RR);
mtx_unlock_spin(&icu_lock);
if ((isr & IRQ_MASK(7)) == 0)
return;
}
--
John Baldwin
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