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 11:21 AM
> To: Bharat Bhushan <bharat.bhushan@xxxxxxx>; Rob Herring
> <robh@xxxxxxxxxx>
> 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 Wed, 2018-08-08 at 03:37 +0000, Bharat Bhushan wrote:
> > > -----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.
> 
> The driver has been doing this forever with no ill effect.

Yes, there are no issue reported

>  What is the  motivation for this change?

On Simulation model I see warning when accessing the reserved region, So this patch is just an effort to improve.

Thanks
-Bharat

> 
> -Scott