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arm64/lib: add accelerated crc32 routines

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Unlike crc32c(), which is wired up to the crypto API internally so the
optimal driver is selected based on the platform's capabilities,
crc32_le() is implemented as a library function using a slice-by-8 table
based C implementation. Even though few of the call sites may be
bottlenecks, calling a time variant implementation with a non-negligible
D-cache footprint is a bit of a waste, given that ARMv8.1 and up mandates
support for the CRC32 instructions that were optional in ARMv8.0, but are
already widely available, even on the Cortex-A53 based Raspberry Pi.

So implement routines that use these instructions if available, and fall
back to the existing generic routines otherwise. The selection is based
on alternatives patching.

Note that this unconditionally selects CONFIG_CRC32 as a builtin. Since
CRC32 is relied upon by core functionality such as CONFIG_OF_FLATTREE,
this just codifies the status quo.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Ard Biesheuvel 2018-08-27 13:02:44 +02:00 committed by Catalin Marinas
parent 86d0dd34ea
commit 7481cddf29
3 changed files with 63 additions and 0 deletions
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1
arch/arm64/Kconfig
View File

@ -75,6 +75,7 @@ config ARM64
select CLONE_BACKWARDS
select COMMON_CLK
select CPU_PM if (SUSPEND || CPU_IDLE)
select CRC32
select DCACHE_WORD_ACCESS
select DMA_DIRECT_OPS
select EDAC_SUPPORT

2
arch/arm64/lib/Makefile
View File

@ -25,3 +25,5 @@ KCOV_INSTRUMENT_atomic_ll_sc.o := n
UBSAN_SANITIZE_atomic_ll_sc.o := n
lib-$(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) += uaccess_flushcache.o
obj-$(CONFIG_CRC32) += crc32.o

60
arch/arm64/lib/crc32.S Normal file
View File

@ -0,0 +1,60 @@
/*
* Accelerated CRC32(C) using AArch64 CRC instructions
*
* Copyright (C) 2016 - 2018 Linaro Ltd <ard.biesheuvel@linaro.org>
*
* 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.
*/
#include <linux/linkage.h>
#include <asm/alternative.h>
#include <asm/assembler.h>
.cpu generic+crc
.macro __crc32, c
0: subs x2, x2, #16
b.mi 8f
ldp x3, x4, [x1], #16
CPU_BE( rev x3, x3 )
CPU_BE( rev x4, x4 )
crc32\c\()x w0, w0, x3
crc32\c\()x w0, w0, x4
b.ne 0b
ret
8: tbz x2, #3, 4f
ldr x3, [x1], #8
CPU_BE( rev x3, x3 )
crc32\c\()x w0, w0, x3
4: tbz x2, #2, 2f
ldr w3, [x1], #4
CPU_BE( rev w3, w3 )
crc32\c\()w w0, w0, w3
2: tbz x2, #1, 1f
ldrh w3, [x1], #2
CPU_BE( rev16 w3, w3 )
crc32\c\()h w0, w0, w3
1: tbz x2, #0, 0f
ldrb w3, [x1]
crc32\c\()b w0, w0, w3
0: ret
.endm
.align 5
ENTRY(crc32_le)
alternative_if_not ARM64_HAS_CRC32
b crc32_le_base
alternative_else_nop_endif
__crc32
ENDPROC(crc32_le)
.align 5
ENTRY(__crc32c_le)
alternative_if_not ARM64_HAS_CRC32
b __crc32c_le_base
alternative_else_nop_endif
__crc32 c
ENDPROC(__crc32c_le)