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From:   Scott Wood <oss@buserror.net>
To:     Bharat Bhushan <bharat.bhushan@nxp.com>,
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Date:   Thu, 09 Aug 2018 01:11:55 -0500
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Subject: Re: [RFC 5/5] powerpc/fsl: Add supported-irq-ranges for P2020
Sender: linux-kernel-owner@vger.kernel.org
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On Thu, 2018-08-09 at 03:28 +0000, Bharat Bhushan wrote:
> > -----Original Message-----
> > From: Scott Wood [mailto:oss@buserror.net]
> > Sent: Wednesday, August 8, 2018 11:27 PM
> > To: Bharat Bhushan <bharat.bhushan@nxp.com>;
> > benh@kernel.crashing.org; paulus@samba.org; mpe@ellerman.id.au;
> > galak@kernel.crashing.org; mark.rutland@arm.com;
> > kstewart@linuxfoundation.org; gregkh@linuxfoundation.org;
> > devicetree@vger.kernel.org; linuxppc-dev@lists.ozlabs.org; linux-
> > kernel@vger.kernel.org
> > Cc: robh@kernel.org; keescook@chromium.org; tyreld@linux.vnet.ibm.com;
> > joe@perches.com
> > Subject: Re: [RFC 5/5] powerpc/fsl: Add supported-irq-ranges for P2020
> > 
> > On Wed, 2018-08-08 at 06:28 +0000, Bharat Bhushan wrote:
> > > > -----Original Message-----
> > > > From: Scott Wood [mailto:oss@buserror.net]
> > > > Sent: Wednesday, August 8, 2018 11:26 AM
> > > > To: Bharat Bhushan <bharat.bhushan@nxp.com>;
> > > > benh@kernel.crashing.org; paulus@samba.org; mpe@ellerman.id.au;
> > > > galak@kernel.crashing.org; mark.rutland@arm.com;
> > > > kstewart@linuxfoundation.org; gregkh@linuxfoundation.org;
> > > > devicetree@vger.kernel.org; linuxppc-dev@lists.ozlabs.org; linux-
> > > > kernel@vger.kernel.org
> > > > Cc: robh@kernel.org; keescook@chromium.org;
> > > > tyreld@linux.vnet.ibm.com; joe@perches.com
> > > > Subject: Re: [RFC 5/5] powerpc/fsl: Add supported-irq-ranges for
> > > > P2020
> > > > 
> > > > On Wed, 2018-08-08 at 03:44 +0000, Bharat Bhushan wrote:
> > > > > > -----Original Message-----
> > > > > > From: Scott Wood [mailto:oss@buserror.net]
> > > > > > Sent: Wednesday, August 8, 2018 2:44 AM
> > > > > > To: Bharat Bhushan <bharat.bhushan@nxp.com>;
> > > > > > benh@kernel.crashing.org; paulus@samba.org; mpe@ellerman.id.au;
> > > > > > galak@kernel.crashing.org; mark.rutland@arm.com;
> > > > > > kstewart@linuxfoundation.org; gregkh@linuxfoundation.org;
> > > > > > devicetree@vger.kernel.org; linuxppc-dev@lists.ozlabs.org;
> > > > > > linux- kernel@vger.kernel.org
> > > > > > Cc: robh@kernel.org; keescook@chromium.org;
> > > > > > tyreld@linux.vnet.ibm.com; joe@perches.com
> > > > > > Subject: Re: [RFC 5/5] powerpc/fsl: Add supported-irq-ranges for
> > > > > > P2020
> > > > > > 
> > > > > > On Fri, 2018-07-27 at 15:18 +0530, Bharat Bhushan wrote:
> > > > > > > MPIC on NXP (Freescale) P2020 supports following irq
> > > > > > > ranges:
> > > > > > >   > 0 - 11      (External interrupt)
> > > > > > >   > 16 - 79     (Internal interrupt)
> > > > > > >   > 176 - 183   (Messaging interrupt)
> > > > > > >   > 224 - 231   (Shared message signaled interrupt)
> > > > > > 
> > > > > > Why don't you convert to the 4-cell interrupt specifiers that
> > > > > > make dealing with these ranges less error-prone?
> > > > > 
> > > > > Ok , will do if we agree to have this series as per comment on
> > > > > other patch.
> > > > 
> > > > If you're concerned with errors, this would be a good things to do
> > > > regardless.
> > > >  Actually, it seems that p2020si-post.dtsi already uses 4-cell
> > > > interrupts.
> > > > 
> > > > What is motivating this patchset?  Is there something wrong in the
> > > > existing dts files?
> > > 
> > > There is no error in device tree. Main motivation is to improve code
> > > for following reasons:
> > >   - While code study it was found that if a reserved irq-number used
> > > then there are no check in driver. irq will be configured as correct
> > > and interrupt will never fire.
> > 
> > Again, a wrong interrupt number won't fire, whether an interrupt by that
> > number exists or not.  I wouldn't mind a sanity check in the driver if the
> > programming model made it properly discoverable, but I don't think it's
> > worth messing with device trees just for this (and even less so given that
> > there don't seem to be new chips coming out that this would be relevant
> > for).
> 
> Fair enough, we can use MPIC version to define supported interrupts ranges.
> Will that be acceptable.

It's better than device tree changes but I'm not convinced it's worthwhile
just to suppress some simulator warnings.  If the warnings really bother you,
you can use pic-no-reset in the device tree (assuming this isn't some new chip
that you want to make sure doesn't fall over when the usual mpic init happens)
and/or convince the hardware people to make the interface properly
discoverable including discontiguous regions (if there *is* some new chip I
haven't heard about).

-Scott