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

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Date:   Wed, 8 Aug 2018 06:28:09 +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: 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.
 - Warnings were observed on development platform (simulator) when read/write to reserved MPIC reason during init.
  
> 
> 
> >
> > >
> > > > diff --git a/arch/powerpc/platforms/85xx/mpc85xx_rdb.c
> > > > b/arch/powerpc/platforms/85xx/mpc85xx_rdb.c
> > > > index 1006950..49ff348 100644
> > > > --- a/arch/powerpc/platforms/85xx/mpc85xx_rdb.c
> > > > +++ b/arch/powerpc/platforms/85xx/mpc85xx_rdb.c
> > > > @@ -57,6 +57,11 @@ void __init mpc85xx_rdb_pic_init(void)
> > > >  			MPIC_BIG_ENDIAN |
> > > >  			MPIC_SINGLE_DEST_CPU,
> > > >  			0, 256, " OpenPIC  ");
> > > > +	} else if (of_machine_is_compatible("fsl,P2020RDB-PC")) {
> > > > +		mpic = mpic_alloc(NULL, 0,
> > > > +		  MPIC_BIG_ENDIAN |
> > > > +		  MPIC_SINGLE_DEST_CPU,
> > > > +		  0, 0, " OpenPIC  ");
> > > >  	} else {
> > > >  		mpic = mpic_alloc(NULL, 0,
> > > >  		  MPIC_BIG_ENDIAN |
> > >
> > > I don't think we want to grow a list of every single revision of
> > > every board in these platform files.
> >
> > One other confusing observation I have is that "irq_count" from
> > platform code is given precedence over "last-interrupt-source" in device-
> tree.
> > Should not device-tree should have precedence otherwise there is no
> > point using " last-interrupt-source" if platform code passes
> > "irq_count" in mpic_alloc().
> 
> Maybe, though I don't think it matters much given that last-interrupt-source
> was only added to avoid having to pass irq_count in platform code.

Thanks for clarifying;

My understanding was that "last-interrupt-source" added to ensure that we can over-ride value passed from platform code. In that case we do not need to change code and can control from device tree.

Thanks
-Bharat


> 
> -Scott