linux-kernel - RE: [PATCH] powerpc/mpic: Cleanup irq vector accounting

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Date:   Thu, 5 Jul 2018 15:42:44 +0000
From:   Bharat Bhushan <bharat.bhushan@....com>
To:     Michael Ellerman <mpe@...erman.id.au>,
        "benh@...nel.crashing.org" <benh@...nel.crashing.org>,
        "paulus@...ba.org" <paulus@...ba.org>,
        "robh@...nel.org" <robh@...nel.org>,
        "geoff@...radead.org" <geoff@...radead.org>,
        "tyreld@...ux.vnet.ibm.com" <tyreld@...ux.vnet.ibm.com>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] powerpc/mpic: Cleanup irq vector accounting



> -----Original Message-----
> From: Michael Ellerman [mailto:mpe@...erman.id.au]
> Sent: Wednesday, July 4, 2018 6:57 PM
> To: Bharat Bhushan <bharat.bhushan@....com>;
> benh@...nel.crashing.org; paulus@...ba.org; robh@...nel.org;
> geoff@...radead.org; tyreld@...ux.vnet.ibm.com; linuxppc-
> dev@...ts.ozlabs.org; linux-kernel@...r.kernel.org
> Cc: Bharat Bhushan <bharat.bhushan@....com>
> Subject: Re: [PATCH] powerpc/mpic: Cleanup irq vector accounting
> 
> Bharat Bhushan <Bharat.Bhushan@....com> writes:
> 
> > Available vector space accounts ipis and timer interrupts while
> > spurious vector was not accounted.
> 
> OK. What is the symptom of that? Nothing? Total system crash?
> 
> Looks like this can be tagged:
> 
> Fixes: 0a4081641d72 ("powerpc/mpic: FSL MPIC error interrupt support.")
> 
> Which added the code that uses "12".
> 
> > Also later
> > mpic_setup_error_int() escape one more vector, seemingly it assumes
> > one spurious vector.
> 
> Ah right, I get it now.
> 
> So there is no bug. It's just a disagreement about whether the "intvec"
> argument to mpic_setup_error_int() indicates the first number that's free to
> use or the last number that has been allocated.
> 
> Right?

Yes, it is not any bug fix. This is minor cleanup where passing rather than passing "last intvec used" to "intvec to be used" in mpic_setup_error_int().

Thanks
-Bharat

> 
> cheers
> 
> > Signed-off-by: Bharat Bhushan <Bharat.Bhushan@....com>
> > ---
> >  arch/powerpc/sysdev/fsl_mpic_err.c | 2 +-
> >  arch/powerpc/sysdev/mpic.c         | 6 +++---
> >  2 files changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/powerpc/sysdev/fsl_mpic_err.c
> > b/arch/powerpc/sysdev/fsl_mpic_err.c
> > index 488ec45..2a98837 100644
> > --- a/arch/powerpc/sysdev/fsl_mpic_err.c
> > +++ b/arch/powerpc/sysdev/fsl_mpic_err.c
> > @@ -76,7 +76,7 @@ int mpic_setup_error_int(struct mpic *mpic, int
> intvec)
> >  	mpic->flags |= MPIC_FSL_HAS_EIMR;
> >  	/* allocate interrupt vectors for error interrupts */
> >  	for (i = MPIC_MAX_ERR - 1; i >= 0; i--)
> > -		mpic->err_int_vecs[i] = --intvec;
> > +		mpic->err_int_vecs[i] = intvec--;
> >
> >  	return 0;
> >  }
> > diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
> > index 1d4e0ef6..e098d1e 100644
> > --- a/arch/powerpc/sysdev/mpic.c
> > +++ b/arch/powerpc/sysdev/mpic.c
> > @@ -1380,12 +1380,12 @@ struct mpic * __init mpic_alloc(struct
> device_node *node,
> >  		 * global vector number space, as in case of ipis
> >  		 * and timer interrupts.
> >  		 *
> > -		 * Available vector space = intvec_top - 12, where 12
> > +		 * Available vector space = intvec_top - 13, where 13
> >  		 * is the number of vectors which have been consumed by
> > -		 * ipis and timer interrupts.
> > +		 * ipis, timer interrupts and spurious.
> >  		 */
> >  		if (fsl_version >= 0x401) {
> > -			ret = mpic_setup_error_int(mpic, intvec_top - 12);
> > +			ret = mpic_setup_error_int(mpic, intvec_top - 13);
> >  			if (ret)
> >  				return NULL;
> >  		}
> > --
> > 1.9.3