linux-kernel - Re: [PATCH 4/4] arm64: add early

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Message-ID: <20131216144246.GG17713@arm.com>
Date:	Mon, 16 Dec 2013 14:42:46 +0000
From:	Catalin Marinas <catalin.marinas@....com>
To:	Mark Salter <msalter@...hat.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Leif Lindholm <leif.lindholm@...aro.org>,
	Will Deacon <Will.Deacon@....com>,
	Rob Landley <rob@...dley.net>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH 4/4] arm64: add early_ioremap support

On Fri, Dec 06, 2013 at 05:20:49PM +0000, Mark Salter wrote:
> On Thu, 2013-12-05 at 16:28 +0000, Catalin Marinas wrote:
> > On Thu, Nov 28, 2013 at 02:44:39AM +0000, Mark Salter wrote:
> > > + * These 'compile-time allocated' memory buffers are
> > > + * page-sized. Use set_fixmap(idx,phys) to associate
> > > + * physical memory with fixmap indices.
> > > + *
> > > + */
> > > +enum fixed_addresses {
> > > +	FIX_EARLYCON,
> > > +	__end_of_permanent_fixed_addresses,
> > > +
> > > +	/*
> > > +	 * Temporary boot-time mappings, used by early_ioremap(),
> > > +	 * before ioremap() is functional.
> > > +	 */
> > 
> > How temporary are this mappings? The early console may not be disabled
> > at run-time, so it still needs the mapping.
> 
> It varies by arch, but we have flexibility on arm64 because there is a
> dedicated pmd which stays around forever. So, you see the FIX_EARLYCON
> above is a "permanent" mapping which isn't really an early_ioremap
> mapping. The earlyprintk code uses set_fixmap_io. I suppose this could
> have been broken up into two patches, one fixmap, and one early_ioremap.
> To answer your concern, the earlyprintk mapping doesn't go away. The
> early_ioremap mappings should be temporary and there's a checker for
> that which is run at late_initcall time.

OK, thanks for clarification, I don't think it's worth splitting the
patch.

-- 
Catalin
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