This change implements an optimized checksum for arm64, based loosely on the original arch/arm implementation. Load-pair is used for the initial 16B load, reducing the overall number of loads to two for packets without IP options. Instruction count is reduced by ~3x compared to generic C implementation. Changes were tested against LE and BE operation and for all possible mis-alignments.
Signed-off-by: Luke Starrett <[email protected]> --- arch/arm64/include/asm/checksum.h | 57 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) create mode 100644 arch/arm64/include/asm/checksum.h diff --git a/arch/arm64/include/asm/checksum.h b/arch/arm64/include/asm/checksum.h new file mode 100644 index 0000000..15629d7 --- /dev/null +++ b/arch/arm64/include/asm/checksum.h @@ -0,0 +1,57 @@ +/* + * Copyright 2016 Broadcom + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License, version 2, as + * published by the Free Software Foundation (the "GPL"). + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License version 2 (GPLv2) for more details. + * + * You should have received a copy of the GNU General Public License + * version 2 (GPLv2) along with this source code. + * + * ip_fast_csum() loosely derived from original arch/arm implementation + */ + +#ifndef __ASM_ARM64_CHECKSUM_H +#define __ASM_ARM64_CHECKSUM_H + +/* + * This is a version of ip_compute_csum() optimized for IP headers, + * which always checksum on 4 octet boundaries. + */ +static inline __sum16 +ip_fast_csum(const void *iph, unsigned int ihl) +{ + u64 tmp, sum; + + __asm__ __volatile__ ( +" ldp %0, %3, [%1], #16\n" +" sub %2, %2, #4\n" +" adds %0, %0, %3\n" +"1: ldr %w3, [%1], #4\n" +" sub %2, %2, #1\n" +" adcs %0, %0, %3\n" +" tst %2, #15\n" +" bne 1b\n" +" adc %0, %0, xzr\n" +" ror %3, %0, #32\n" +" add %0, %0, %3\n" +" lsr %0, %0, #32\n" +" ror %w3, %w0, #16\n" +" add %w0, %w0, %w3\n" +" lsr %0, %0, #16\n" + : "=r" (sum), "=r" (iph), "=r" (ihl), "=r" (tmp) + : "1" (iph), "2" (ihl) + : "cc", "memory"); + + return (__force __sum16)(~sum); +} + +#define ip_fast_csum ip_fast_csum +#include <asm-generic/checksum.h> + +#endif /* __ASM_ARM64_CHECKSUM_H */ -- 2.1.0
