IRQ numbering (was: Better timer and RTC handling for 8641HPCN.)

[Zhang Wei-r63237]

> >>>>> Please use 80.
> >>>>> We reserve the first 16 ints for legacy 8259 interrupts. And we
> >>>>> want the
> >>>>> virq is the same value to hw-irq.
> >>>>
> >>>> Why?
> >>>
> >>> If the virq equals hw-irq, it's clear and simple to user.
> >>
> >> I don't think that's a good reason to over allocate.
> >>
> >> There's a reason we have virtual IRQs now.  Its 
> specifically to deal
> >> with issues like the 16 interrupts for 8259 and not have 
> to do games
> >> to offset IRQs.
> >>
> >> If we needed create some debugfs or sysfs info that translates VIRQ
> >> to HW irq
> >>
> >
> > I know that's the advantage of virtual IRQs. But in this 
> platform, we
> > want to fix up the virq to hwirq and let users know which irq is  
> > coming
> > from which devices.
> 
> But how do I know IRQ 42 is really 26 for the MPIC.  What are you  
> users doing that they can't handle the virtual irq concept?
> 
> It was pointed out, that you are coupling the IRQ # in the .dts with  
> the kernel virtual number which is a bad idea.  In theory the device- 
> tree description shouldn't be coupled this tightly to the kernel.
> 
> I think the Freescale reference boards should strive to show people  
> how to do things properly since people tend to copy this code 
> and use  
> it as a starting point.  I doubt most 86xx designs are really going  
> to have an 8259 controller on them and thus making things focus  
> around it seems silly.
> 
Hi, Kumar,

I have used the a fake interrupt hole to avoid the hwirq overlapping.
Now the virq equals the hwirq. 

I agree with the virq has lots of advantages than irq offset. But we can
not give the user a fixup irq list since the virq will be changed by
different device driver loading. And the user can not get the hwirq from
the user space application.

I think creating some debugfs or sysfs info that translates VIRQ to HW
irq is a _good_ idea, or just add some fields (irq host, hwirq) in
/proc/interrupts. If we have this, I'll fix all irqs in dts file and
remove the fake irq hole.

Before we have a virq-hwirq mapping list, I keep my option about the irq
number.

Thanks!
Zhang Wei