linux-kernel - Re: [PATCH v2 1/4] arch/*/asm/io.h: add ioremap

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Date:	Tue, 2 Jun 2015 10:38:48 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Toshi Kani <toshi.kani@...com>,
	Dan Williams <dan.j.williams@...el.com>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	ross.zwisler@...ux.intel.com,
	Andrew Morton <akpm@...ux-foundation.org>, jgross@...e.com,
	"the arch/x86 maintainers" <x86@...nel.org>,
	linux-nvdimm@...ts.01.org, "Luis R. Rodriguez" <mcgrof@...e.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	stefan.bader@...onical.com, Andy Lutomirski <luto@...capital.net>,
	Linux MM <linux-mm@...ck.org>,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	Tejun Heo <tj@...nel.org>, Christoph Hellwig <hch@....de>,
	David Howells <dhowells@...hat.com>
Subject: Re: [PATCH v2 1/4] arch/*/asm/io.h: add ioremap_cache() to all architectures

On Tue, Jun 2, 2015 at 10:20 AM, Arnd Bergmann <arnd@...db.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@...ux-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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