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Date: Tue, 2 Jun 2015 10:38:48 +0200
Message-ID: <CAMuHMdXXXEqaGf1zT0iL=K-LA3qcnx9aCJLZnC6W3ijY4dRipQ@mail.gmail.com>
Subject: Re: [PATCH v2 1/4] arch/*/asm/io.h: add ioremap_cache() to all architectures
From: Geert Uytterhoeven <geert@linux-m68k.org>
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Sender: owner-linux-mm@kvack.org
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To: Arnd Bergmann <arnd@arndb.de>
Cc: Toshi Kani <toshi.kani@hp.com>, Dan Williams <dan.j.williams@intel.com>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>, ross.zwisler@linux.intel.com, Andrew Morton <akpm@linux-foundation.org>, jgross@suse.com, the arch/x86 maintainers <x86@kernel.org>, linux-nvdimm@lists.01.org, "Luis R. Rodriguez" <mcgrof@suse.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, stefan.bader@canonical.com, Andy Lutomirski <luto@amacapital.net>, Linux MM <linux-mm@kvack.org>, Henrique de Moraes Holschuh <hmh@hmh.eng.br>, Tejun Heo <tj@kernel.org>, Christoph Hellwig <hch@lst.de>, David Howells <dhowells@redhat.com>

On Tue, Jun 2, 2015 at 10:20 AM, Arnd Bergmann <arnd@arndb.de> wrote:
>> > --- a/arch/mn10300/include/asm/io.h
>> > +++ b/arch/mn10300/include/asm/io.h
>> > @@ -283,6 +283,7 @@ static inline void __iomem *ioremap_nocache(unsigned long offset, unsigned long
>> >
>> >  #define ioremap_wc ioremap_nocache
>> >  #define ioremap_wt ioremap_nocache
>> > +#define ioremap_cache ioremap_nocache
>>
>> From the comment in ioremap_nocache(), ioremap() may be cacheable in
>> this arch.
>
> Right, and I guess that would be a bug. ;-)
>
> mn10300 decides caching on the address, so presumably all arguments passed into

Aha, like MIPS...

> ioremap here already have that bit set. I've checked all the resource
> definitions for mn10300, and they are all between 0xA0000000 and 0xBFFFFFFF,
> which is non-cacheable.

But ioremap() clears that bit again:

static inline void __iomem *ioremap(unsigned long offset, unsigned long size)
{
        return (void __iomem *)(offset & ~0x20000000);
}

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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