Subject: Re: Interrupt prioritization on linux for ppc440

From: Eugene Surovegin <[email-masked]>
Date: Fri, 15 Apr 2005 15:12:35 -0700

On Fri, Apr 15, 2005 at 02:36:51PM -0700, Shawn Jin wrote:
> 
> The home-made interrupt controller PIC supports interrupt priorities
> and critical/non-critical interrupts. I found that the current kernel
> doesn't support interrupt priorities. 

Yes, we don't have IRQ priorities on 4xx. Theoretically, they can be 
emulated in get_irq, but I really don't think it's worth it.

> Is this observation true? Is
> there any existing patch to support that? 

I'm not aware of such patch existence.

> I noticed that the implementation of ppc4xx_pic.c disables all
> critical interrupts during initialization. To support critical
> interrupts, is it so simple that we change the handler of critical
> exception from CriticalInput to do_IRQ in head_44x.S?

No, it's not that simple. Linux doesn't support a notion of critical 
IRQs versus normal ones. Until there is an infrastructure for this, it 
doesn't make any sense to implement 4xx support.

--
Eugene