linux-kernel - Re: [PATCH] arm64: allow late use of early

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Message-ID: <1421089778.12632.2.camel@t520.localdomain>
Date:	Mon, 12 Jan 2015 14:09:38 -0500
From:	Mark Salter <msalter@...hat.com>
To:	Will Deacon <will.deacon@....com>
Cc:	Catalin Marinas <Catalin.Marinas@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Leif Lindholm <leif.lindholm@...aro.org>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: Re: [PATCH] arm64: allow late use of early_ioremap

On Mon, 2015-01-12 at 17:25 +0000, Will Deacon wrote:
> On Mon, Jan 12, 2015 at 04:55:11PM +0000, Mark Salter wrote:
> > Commit 0e63ea48b4d8 (arm64/efi: add missing call to early_ioremap_reset())
> > added a missing call to early_ioremap_reset(). This triggers a BUG if code
> > tries using early_ioremap() after the early_ioremap_reset(). This is a
> > problem for some ACPI code which needs short-lived temporary mappings
> > after paging_init() but before mm_init(). This patch adds definitions for
> > the __late_set_fixmap() and __late_clear_fixmap() which avoids the BUG
> > by allowing later use of early_ioremap().
> > 
> > Signed-off-by: Mark Salter <msalter@...hat.com>
> > CC: Leif Lindholm <leif.lindholm@...aro.org>
> > CC: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> > ---
> >  arch/arm64/include/asm/fixmap.h | 3 +++
> >  1 file changed, 3 insertions(+)
> 
> Given that we don't support ACPI on arm64 in mainline, I assume this can
> wait until at least 3.20?

Sure. Just needs it to go in before ACPI code. And tbh, the ACPI code
could change and make this unneeded.

> 
> Will
> 
> > diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h
> > index 9ef6eca..e629c70 100644
> > --- a/arch/arm64/include/asm/fixmap.h
> > +++ b/arch/arm64/include/asm/fixmap.h
> > @@ -61,6 +61,9 @@ void __init early_fixmap_init(void);
> >  
> >  #define __early_set_fixmap __set_fixmap
> >  
> > +#define __late_set_fixmap __set_fixmap
> > +#define __late_clear_fixmap(idx) __set_fixmap((idx), 0, FIXMAP_PAGE_CLEAR)
> > +
> >  extern void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot);
> >  
> >  #include <asm-generic/fixmap.h>
> > -- 
> > 1.8.3.1
> > 
> > 


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