From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Fri, 8 Jun 2012 16:38:55 +0100 Subject: [RFC PATCH 2/2] ARM: dcache: select DCACHE_WORD_ACCESS for little-endian ARMv6+ CPUs In-Reply-To: <1339169935-31775-1-git-send-email-will.deacon@arm.com> References: <1339169935-31775-1-git-send-email-will.deacon@arm.com> Message-ID: <1339169935-31775-3-git-send-email-will.deacon@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. Signed-off-by: Will Deacon --- arch/arm/Kconfig | 1 + arch/arm/include/asm/word-at-a-time.h | 41 +++++++++++++++++++++++++++++++++ 2 files changed, 42 insertions(+), 0 deletions(-) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index b236fd9..9e7b51f 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -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 diff --git a/arch/arm/include/asm/word-at-a-time.h b/arch/arm/include/asm/word-at-a-time.h index 74b2d45..4d52f92 100644 --- a/arch/arm/include/asm/word-at-a-time.h +++ b/arch/arm/include/asm/word-at-a-time.h @@ -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 #endif -- 1.7.4.1