linux-kernel - RE: [RFC 5/5] powerpc/fsl: Add supported-irq-ranges for P2020

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Date:   Thu, 9 Aug 2018 07:04:35 +0000
From:   Bharat Bhushan <bharat.bhushan@....com>
To:     Scott Wood <oss@...error.net>,
        "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>
CC:     "robh@...nel.org" <robh@...nel.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 5/5] powerpc/fsl: Add supported-irq-ranges for P2020



> -----Original Message-----
> From: Scott Wood [mailto:oss@...error.net]
> Sent: Thursday, August 9, 2018 11:42 AM
> To: Bharat Bhushan <bharat.bhushan@....com>;
> 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
> Cc: robh@...nel.org; keescook@...omium.org; tyreld@...ux.vnet.ibm.com;
> joe@...ches.com
> Subject: Re: [RFC 5/5] powerpc/fsl: Add supported-irq-ranges for P2020
> 
> On Thu, 2018-08-09 at 03:28 +0000, Bharat Bhushan wrote:
> > > -----Original Message-----
> > > From: Scott Wood [mailto:oss@...error.net]
> > > Sent: Wednesday, August 8, 2018 11:27 PM
> > > To: Bharat Bhushan <bharat.bhushan@....com>;
> > > 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
> > > Cc: robh@...nel.org; keescook@...omium.org;
> > > tyreld@...ux.vnet.ibm.com; joe@...ches.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@...error.net]
> > > > > Sent: Wednesday, August 8, 2018 11:26 AM
> > > > > To: Bharat Bhushan <bharat.bhushan@....com>;
> > > > > 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
> > > > > Cc: robh@...nel.org; keescook@...omium.org;
> > > > > tyreld@...ux.vnet.ibm.com; joe@...ches.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@...error.net]
> > > > > > > Sent: Wednesday, August 8, 2018 2:44 AM
> > > > > > > To: Bharat Bhushan <bharat.bhushan@....com>;
> > > > > > > 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
> > > > > > > Cc: robh@...nel.org; keescook@...omium.org;
> > > > > > > tyreld@...ux.vnet.ibm.com; joe@...ches.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).

There is new chip under development based on e200, which uses same mpic as in older PowerPC versions.
This patch was not just about suppressing the warning but warning was the observation that reserved region is getting accessed during init/uninit/save/restore. This patch was just an minor improvement to avoid these accesses. We will drop this series if this improvement is not convincing.

Thanks
-Bharat

> 
> -Scott