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ARM: 7450/1: dcache: select DCACHE_WORD_ACCESS for little-endian ARMv6+ CPUs

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DCACHE_WORD_ACCESS uses the word-at-a-time API for optimised string
comparisons in the vfs layer.

This patch implements support for load_unaligned_zeropad for ARM CPUs
with native support for unaligned memory accesses (v6+) when running
little-endian.

Reviewed-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Will Deacon 2012-07-06 15:46:08 +01:00 committed by Russell King
parent 8c56cc8be5
commit b9a50f7490
2 changed files with 42 additions and 0 deletions
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1
arch/arm/Kconfig
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@ -48,6 +48,7 @@ config ARM
select GENERIC_CLOCKEVENTS_BROADCAST if SMP
select GENERIC_STRNCPY_FROM_USER
select GENERIC_STRNLEN_USER
select DCACHE_WORD_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && !CPU_BIG_ENDIAN
help
The ARM series is a line of low-power-consumption RISC chip designs
licensed by ARM Ltd and targeted at embedded applications and

41
arch/arm/include/asm/word-at-a-time.h
View File

@ -48,6 +48,47 @@ static inline unsigned long find_zero(unsigned long mask)
return ret;
}
#ifdef CONFIG_DCACHE_WORD_ACCESS
#define zero_bytemask(mask) (mask)
/*
* Load an unaligned word from kernel space.
*
* In the (very unlikely) case of the word being a page-crosser
* and the next page not being mapped, take the exception and
* return zeroes in the non-existing part.
*/
static inline unsigned long load_unaligned_zeropad(const void *addr)
{
unsigned long ret, offset;
/* Load word from unaligned pointer addr */
asm(
"1: ldr %0, [%2]\n"
"2:\n"
" .pushsection .fixup,\"ax\"\n"
" .align 2\n"
"3: and %1, %2, #0x3\n"
" bic %2, %2, #0x3\n"
" ldr %0, [%2]\n"
" lsl %1, %1, #0x3\n"
" lsr %0, %0, %1\n"
" b 2b\n"
" .popsection\n"
" .pushsection __ex_table,\"a\"\n"
" .align 3\n"
" .long 1b, 3b\n"
" .popsection"
: "=&r" (ret), "=&r" (offset)
: "r" (addr), "Qo" (*(unsigned long *)addr));
return ret;
}
#endif /* DCACHE_WORD_ACCESS */
#else /* __ARMEB__ */
#include <asm-generic/word-at-a-time.h>
#endif