Subject: Re: [PATCH] 3 patches against linuxppc_dev-2.4.18-pre7

From: Armin Kuster <[email-masked]>
Date: Thu, 31 Jan 2002 10:15:46 -0800

"David Müller (ELSOFT AG)" wrote:
>
> Hi
>
> Armin Kuster wrote:
>
> > "David Müller (ELSOFT AG)" wrote:
> >
> >>Hello
> >>
> >>The attached patch fixes the following issues:
> >>
> >>    - arch/ppc/kernel/ppc4xx_pic.c
> >>       fixed constant in ppc405_pic_get_irq()
> >>       (should be NR_AIC_IRQS as in ppc403_pic_get_irq())
> >>
> >
> > David,
> >
> > include/asm-ppc/irq.h
> > NR_IRQS = (NR_AIC_IRQS + NR_BOARD_IRQS) and was defined to allow
> > cascading UIC's.
> > NR_BOARD_IRQS is defined in some of the board files and its default is
> > in include/asm-ppc/ibm4xx.h
> >
> > So i don't see the need to patch that file but the others look fine.
> >
> >
>
> Exactly, NR_IRQS is the the total number of irqs possible in the system
> as this number of irqs is reserved in the irq_desc table.
>
> For example, we have a system with a PPC405GP and an additional PC like 8259 PIC
> pair, we have NR_AIC_IRQS (32) + NR_BOARD_IRQS (16) = NR_IRQS (48).
>
> In ppc405_pic_get_irq() the following code is executed:
>
>         irq = 32 - ffs(bits);
>
>         if (irq == NR_IRQS)
>                 irq = -1;
>
>         return(irq);
>
> with NR_IRQS equal 48 the condition is never true !
>
> This results in an endless while-loop in do_IRQ() in arch/ppc/kernel/irq.c
>
> Either this or my understanding how things are working is totally wrong. ;-)
> Additionally, i don't see me why ppc403_pic_get_irq() is using NC_AIC_IRQS while
> ppc405_pic_get_irq() is using NR_IRQS. Shouldn't they be "symmetric".
>
> Dave

David,

your right.

-- armin

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