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ARM: Avoid compiler optimization for readb, writeb and friends.

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gcc 4.5.1 seems to ignore (at least some) volatile definitions,
avoid that as done in the kernel.

Reading C99 6.7.3 8 and the comment 114) there, I think it is a bug of that
gcc version to ignore the volatile type qualifier used e.g. in __arch_getl().
Anyway, using a definition as in the kernel headers avoids such optimizations when
gcc 4.5.1 is used.

Maybe the headers as used in the current linux-kernel should be used,
but to avoid large changes, I've just added a small change to the current headers.

Signed-off-by: Alexander Holler <holler@ahsoftware.de>
Signed-off-by: Dirk Behme <dirk.behme@googlemail.com>
Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Alessandro Rubini <rubini-list@gnudd.com>
Tested-by: Thomas Weber <weber@corscience.de>
Acked-by: Alexander Holler <holler@ahsoftware.de>
Tested-by: Alexander Holler <holler@ahsoftware.de>
This commit is contained in:
Alexander Holler 2011-01-09 12:19:44 +00:00 committed by Albert Aribaud
parent 3c152165c7
commit 3c0659b535
1 changed files with 20 additions and 12 deletions
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32
arch/arm/include/asm/io.h
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@ -117,21 +117,29 @@ extern inline void __raw_readsl(unsigned int addr, void *data, int longlen)
*buf++ = __arch_getl(addr);
}
#define __raw_writeb(v,a) __arch_putb(v,a)
#define __raw_writew(v,a) __arch_putw(v,a)
#define __raw_writel(v,a) __arch_putl(v,a)
#define __raw_writeb(v,a) __arch_putb(v,a)
#define __raw_writew(v,a) __arch_putw(v,a)
#define __raw_writel(v,a) __arch_putl(v,a)
#define __raw_readb(a) __arch_getb(a)
#define __raw_readw(a) __arch_getw(a)
#define __raw_readl(a) __arch_getl(a)
#define __raw_readb(a) __arch_getb(a)
#define __raw_readw(a) __arch_getw(a)
#define __raw_readl(a) __arch_getl(a)
#define writeb(v,a) __arch_putb(v,a)
#define writew(v,a) __arch_putw(v,a)
#define writel(v,a) __arch_putl(v,a)
/*
* TODO: The kernel offers some more advanced versions of barriers, it might
* have some advantages to use them instead of the simple one here.
*/
#define dmb() __asm__ __volatile__ ("" : : : "memory")
#define __iormb() dmb()
#define __iowmb() dmb()
#define readb(a) __arch_getb(a)
#define readw(a) __arch_getw(a)
#define readl(a) __arch_getl(a)
#define writeb(v,c) ({ __iowmb(); __arch_putb(v,c); v; })
#define writew(v,c) ({ __iowmb(); __arch_putw(v,c); v; })
#define writel(v,c) ({ __iowmb(); __arch_putl(v,c); v; })
#define readb(c) ({ u8 __v = __arch_getb(c); __iormb(); __v; })
#define readw(c) ({ u16 __v = __arch_getw(c); __iormb(); __v; })
#define readl(c) ({ u32 __v = __arch_getl(c); __iormb(); __v; })
/*
* The compiler seems to be incapable of optimising constants