linux-kernel - Re: [PATCH 06/28] nios2: Memory management

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Message-ID: <20140422162432.GA17674@ravnborg.org>
Date:	Tue, 22 Apr 2014 18:24:32 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
Cc:	Tobias Klauser <tklauser@...tanz.ch>,
	Ley Foon Tan <lftan@...era.com>, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	lftan.linux@...il.com, cltang@...esourcery.com
Subject: Re: [PATCH 06/28] nios2: Memory management

On Tue, Apr 22, 2014 at 12:35:22PM -0300, Ezequiel Garcia wrote:
> On Apr 22, Tobias Klauser wrote:
> > On 2014-04-22 at 16:24:43 +0200, Ezequiel Garcia <ezequiel.garcia@...e-electrons.com> wrote:
> > > Hi Ley Foon,
> > > 
> > > On Apr 18, Ley Foon Tan wrote:
> > > > +/*
> > > > + * PAGE_SHIFT determines the page size
> > > > + */
> > > > +#define PAGE_SHIFT	12
> > > > +#define PAGE_SIZE	4096
> > > > +#define PAGE_MASK	(~(PAGE_SIZE - 1))
> > > > +
> > > 
> > > How about something like this:
> > > 
> > > /* PAGE_SHIFT determines the page size */
> > > #define PAGE_SHIFT              12
> > > #define PAGE_SIZE               (_AC(1,UL) << PAGE_SHIFT)
> > > #define PAGE_MASK               (~((1 << PAGE_SHIFT) - 1))
> > > 
> > > Otherwise, the PAGE_SIZE macro above produces some warnings, IIRC.
> > 
> > AFAIR old nios2 GCC versions (the 4.1 version from Windriver, IIRC)
> > would complain about something like the above, that's the reason I added
> > an explicit value for PAGE_SIZE back then.
> > 
> 
> Other than being "pretty" the above fix is to remove a mismatch type
> warning. You can get rid of the warning in different ways:
> 
> ifdef __ASSEMBLY__
> define PAGE_SIZE       4096
> else
> define PAGE_SIZE       4096UL
> endif

The usual way to do this is as follows:
#include <linux/const.h>

#define PAGE_SHIFT   12
#define PAGE_SIZE    (_AC(1, UL) << PAGE_SHIFT)
#define PAGE_MASK    (~(PAGE_SIZE-1))

_AC(1, UL) expands to 1 for assembler and 1UL for C code.

This is also what was suggested above.

Please follow this scheme for nios2 too.

	Sam
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