linux-kernel - RE: [PATCH v2 07/11] powerpc/8xx: macro for handling CPU15 errata

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6D1CACF0E4@AcuExch.aculab.com>
Date:	Tue, 20 Jan 2015 11:43:16 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'leroy christophe' <christophe.leroy@....fr>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	"Michael Ellerman" <mpe@...erman.id.au>,
	"scottwood@...escale.com" <scottwood@...escale.com>
CC:	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 07/11] powerpc/8xx: macro for handling CPU15 errata

From: leroy 
> Le 20/01/2015 12:09, David Laight a écrit :
> >  From Christophe Leroy
> >> Having a macro will help keep clear code.
> > It might remove an #if but it doesn't really help.
> > All it means is that anyone reading the code has to hunt for
> > the definition before proceeding.
> >
> > Some comment about what (and why) the extra code is needed
> > might help.
> The main reason is because of patch 09/11 where we have to duplicate
> this code. I prefer to just duplicate one line rather than duplicate the
> whole code (especially because in v1 of the PATCHset, it was duplicated
> twice):
> 
> -    DO_8xx_CPU15(r11, r10)
> [...]
> #ifdef CONFIG_MODULES
> [...]
> +    DO_8xx_CPU15(r10, r11)
> [...]
> +#else
> +    mfspr    r10, SPRN_SRR0    /* Get effective address of fault */
> +    DO_8xx_CPU15(r11, r10)
> 
> Is this approach wrong ?

I'd call it something that infers 'invalidate adjacent pages'
and then mention that this is needed due to a cpu errata.

	David