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Commit b9a50f74 authored by Will Deacon's avatar Will Deacon Committed by Russell King
Browse files

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



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: default avatarNicolas Pitre <nico@linaro.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 8c56cc8b

arch/arm/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -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

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

+41 −0
Original line number Diff line number Diff line
@@ -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