On Mon, Oct 27, 2014 at 08:02:08AM +0000, Wang, Yalin wrote: > this change add CONFIG_HAVE_ARCH_BITREVERSE config option, > so that we can use arm/arm64 rbit instruction to do bitrev operation > by hardware. > > Signed-off-by: Yalin Wang <[email protected]> > --- > arch/arm/Kconfig | 1 + > arch/arm/include/asm/bitrev.h | 28 ++++++++++++++++++++++++++++ > arch/arm64/Kconfig | 1 + > arch/arm64/include/asm/bitrev.h | 28 ++++++++++++++++++++++++++++ > include/linux/bitrev.h | 9 +++++++++ > lib/Kconfig | 9 +++++++++ > lib/bitrev.c | 2 ++ > 7 files changed, 78 insertions(+) > create mode 100644 arch/arm/include/asm/bitrev.h > create mode 100644 arch/arm64/include/asm/bitrev.h > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index 89c4b5c..426cbcc 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -16,6 +16,7 @@ config ARM > select DCACHE_WORD_ACCESS if HAVE_EFFICIENT_UNALIGNED_ACCESS > select GENERIC_ALLOCATOR > select GENERIC_ATOMIC64 if (CPU_V7M || CPU_V6 || !CPU_32v6K || !AEABI) > + select HAVE_ARCH_BITREVERSE if (CPU_V7M || CPU_V7) > select GENERIC_CLOCKEVENTS_BROADCAST if SMP > select GENERIC_IDLE_POLL_SETUP > select GENERIC_IRQ_PROBE > diff --git a/arch/arm/include/asm/bitrev.h b/arch/arm/include/asm/bitrev.h > new file mode 100644 > index 0000000..c21a5f4 > --- /dev/null > +++ b/arch/arm/include/asm/bitrev.h > @@ -0,0 +1,28 @@ > +#ifndef __ASM_ARM_BITREV_H > +#define __ASM_ARM_BITREV_H > + > +static __always_inline __attribute_const__ u32 __arch_bitrev32(u32 x) > +{ > + if (__builtin_constant_p(x)) { > + x = (x >> 16) | (x << 16); > + x = ((x & 0xFF00FF00) >> 8) | ((x & 0x00FF00FF) << 8); > + x = ((x & 0xF0F0F0F0) >> 4) | ((x & 0x0F0F0F0F) << 4); > + x = ((x & 0xCCCCCCCC) >> 2) | ((x & 0x33333333) << 2); > + return ((x & 0xAAAAAAAA) >> 1) | ((x & 0x55555555) << 1); > + } > + __asm__ ("rbit %0, %1" : "=r" (x) : "r" (x));
I think you need to use %w0 and %w1 here, otherwise you bit-reverse the 64-bit register. Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
