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

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Date:   Wed, 8 Aug 2018 03:37:28 +0000
From:   Bharat Bhushan <bharat.bhushan@....com>
To:     Scott Wood <oss@...error.net>, Rob Herring <robh@...nel.org>
CC:     "benh@...nel.crashing.org" <benh@...nel.crashing.org>,
        "paulus@...ba.org" <paulus@...ba.org>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "galak@...nel.crashing.org" <galak@...nel.crashing.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "kstewart@...uxfoundation.org" <kstewart@...uxfoundation.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "tyreld@...ux.vnet.ibm.com" <tyreld@...ux.vnet.ibm.com>,
        "joe@...ches.com" <joe@...ches.com>
Subject: RE: [RFC 3/5] powerpc/mpic: Add support for non-contiguous irq ranges



> -----Original Message-----
> From: Scott Wood [mailto:oss@...error.net]
> Sent: Wednesday, August 8, 2018 2:34 AM
> To: Rob Herring <robh@...nel.org>; Bharat Bhushan
> <bharat.bhushan@....com>
> Cc: benh@...nel.crashing.org; paulus@...ba.org; mpe@...erman.id.au;
> galak@...nel.crashing.org; mark.rutland@....com;
> kstewart@...uxfoundation.org; gregkh@...uxfoundation.org;
> devicetree@...r.kernel.org; linuxppc-dev@...ts.ozlabs.org; linux-
> kernel@...r.kernel.org; keescook@...omium.org;
> tyreld@...ux.vnet.ibm.com; joe@...ches.com
> 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