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SubjectRe: [PATCH] serial: Use real irq on UART0 (IRQ = 0) on PPC4xx systems
On Monday 20 November 2006 12:42, Alan wrote:
> On Mon, 20 Nov 2006 12:00:36 +0100
> Stefan Roese <> wrote:
> > This patch fixes a problem seen on multiple 4xx platforms, where
> > the UART0 interrupt number is 0. The macro "is_real_interrupt" lead
> > on those systems to not use an real interrupt but the timer based
> > implementation.
> NAK.

I knew it. ;-)

> Zero means "no interrupt" in the Linux space. If you have a physical IRQ
> 0 remap it to a convenient number (eg map IRQ's + 1, or stick it on the
> end). The logical and physical IRQ numbering in Linux don't have to match
> up - and given some platforms have IRQ numbering per bus and the like
> clearly doesn't in many cases.

Let's see, if I got this right. You mean that on such a platform, where 0 is a
valid physical IRQ, we should assign another value as virtual IRQ number (not
0 and not -1 of course). And then the platform "pic" implementation should
take care of the remapping of these virtual IRQ numbers to the physical


Best regards,
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