RE: [RFC 3/5] powerpc/mpic: Add support for non-contiguous irq ranges

[Bharat Bhushan]

> -----Original Message-----
> From: Scott Wood [mailto:oss@xxxxxxxxxxxx]
> Sent: Wednesday, August 8, 2018 2:34 AM
> To: Rob Herring <robh@xxxxxxxxxx>; Bharat Bhushan
> <bharat.bhushan@xxxxxxx>
> Cc: benh@xxxxxxxxxxxxxxxxxxx; paulus@xxxxxxxxx; mpe@xxxxxxxxxxxxxx;
> galak@xxxxxxxxxxxxxxxxxxx; mark.rutland@xxxxxxx;
> kstewart@xxxxxxxxxxxxxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx; linuxppc-dev@xxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; keescook@xxxxxxxxxxxx;
> tyreld@xxxxxxxxxxxxxxxxxx; joe@xxxxxxxxxxx
> Subject: Re: [RFC 3/5] powerpc/mpic: Add support for non-contiguous irq
> ranges
> 
> On Tue, 2018-08-07 at 12:09 -0600, Rob Herring wrote:
> > On Fri, Jul 27, 2018 at 03:17:59PM +0530, Bharat Bhushan wrote:
> > > Freescale MPIC h/w may not support all interrupt sources reported by
> > > hardware, "last-interrupt-source" or platform. On these platforms a
> > > misconfigured device tree that assigns one of the reserved
> > > interrupts leaves a non-functioning system without warning.
> >
> > There are lots of ways to misconfigure DTs. I don't think this is
> > special and needs a property.
> 
> Yeah, the system will be just as non-functioning if you specify a valid-but-
> wrong-for-the-device interrupt number.

Some is one additional benefits of this changes, MPIC have reserved regions for un-supported interrupts and read/writes to these reserved regions seams have no effect.
MPIC driver reads/writes to the reserved regions during init/uninit and save/restore state.

Let me know if it make sense to have these changes for mentioned reasons.

Thanks
-Bharat

> 
> >  We've had some interrupt mask or valid properties in the past, but
> > generally don't accept those.
> 
> FWIW, some of them like protected-sources and mpic-msgr-receive-mask
> aren't for detecting errors, but are for partitioning (though the former is
> obsolete with pic-no-reset).
> 
> -Scott