arm64/lib: add accelerated crc32 routines

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>

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1b1a0e9..b4c1f1f 100644 (file)
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -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

diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile
index 68755fd..f28f91f 100644 (file)
--- a/arch/arm64/lib/Makefile
+++ b/arch/arm64/lib/Makefile
@@ -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

diff --git a/arch/arm64/lib/crc32.S b/arch/arm64/lib/crc32.S
new file mode 100644 (file)
index 0000000..5bc1e85
--- /dev/null
+++ b/arch/arm64/lib/crc32.S
@@ -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)