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arm64: bitops: patch in lse instructions when supported by the CPU

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On CPUs which support the LSE atomic instructions introduced in ARMv8.1,
it makes sense to use them in preference to ll/sc sequences.

This patch introduces runtime patching of our bitops functions so that
LSE atomic instructions are used instead.

Reviewed-by: Steve Capper <steve.capper@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Will Deacon 2015-02-12 04:17:37 +00:00
parent 81bb5c6420
commit 084f903727
2 changed files with 45 additions and 21 deletions
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23
arch/arm64/include/asm/lse.h
View File

@ -4,10 +4,19 @@
#if defined(CONFIG_AS_LSE) && defined(CONFIG_ARM64_LSE_ATOMICS)
#include <linux/stringify.h>
#include <asm/alternative.h>
#include <asm/cpufeature.h>
#ifdef __ASSEMBLER__
.arch_extension lse
.macro alt_lse, llsc, lse
alternative_insn "\llsc", "\lse", ARM64_CPU_FEAT_LSE_ATOMICS
.endm
#else /* __ASSEMBLER__ */
__asm__(".arch_extension lse");
/* Move the ll/sc atomics out-of-line */
@ -22,7 +31,16 @@ __asm__(".arch_extension lse");
#define ARM64_LSE_ATOMIC_INSN(llsc, lse) \
ALTERNATIVE(llsc, lse, ARM64_CPU_FEAT_LSE_ATOMICS)
#else
#endif /* __ASSEMBLER__ */
#else /* CONFIG_AS_LSE && CONFIG_ARM64_LSE_ATOMICS */
#ifdef __ASSEMBLER__
.macro alt_lse, llsc, lse
\llsc
.endm
#else /* __ASSEMBLER__ */
#define __LL_SC_INLINE static inline
#define __LL_SC_PREFIX(x) x
@ -30,5 +48,6 @@ __asm__(".arch_extension lse");
#define ARM64_LSE_ATOMIC_INSN(llsc, lse) llsc
#endif /* __ASSEMBLER__ */
#endif /* CONFIG_AS_LSE && CONFIG_ARM64_LSE_ATOMICS */
#endif /* __ASM_LSE_H */

43
arch/arm64/lib/bitops.S
View File

@ -18,52 +18,57 @@
#include <linux/linkage.h>
#include <asm/assembler.h>
#include <asm/lse.h>
/*
* x0: bits 5:0 bit offset
* bits 31:6 word offset
* x1: address
*/
.macro bitop, name, instr
.macro bitop, name, llsc, lse
ENTRY( \name )
and w3, w0, #63 // Get bit offset
eor w0, w0, w3 // Clear low bits
mov x2, #1
add x1, x1, x0, lsr #3 // Get word offset
lsl x3, x2, x3 // Create mask
1: ldxr x2, [x1]
\instr x2, x2, x3
stxr w0, x2, [x1]
cbnz w0, 1b
alt_lse "1: ldxr x2, [x1]", "\lse x3, [x1]"
alt_lse " \llsc x2, x2, x3", "nop"
alt_lse " stxr w0, x2, [x1]", "nop"
alt_lse " cbnz w0, 1b", "nop"
ret
ENDPROC(\name )
.endm
.macro testop, name, instr
.macro testop, name, llsc, lse
ENTRY( \name )
and w3, w0, #63 // Get bit offset
eor w0, w0, w3 // Clear low bits
mov x2, #1
add x1, x1, x0, lsr #3 // Get word offset
lsl x4, x2, x3 // Create mask
1: ldxr x2, [x1]
lsr x0, x2, x3 // Save old value of bit
\instr x2, x2, x4 // toggle bit
stlxr w5, x2, [x1]
cbnz w5, 1b
dmb ish
alt_lse "1: ldxr x2, [x1]", "\lse x4, x2, [x1]"
lsr x0, x2, x3
alt_lse " \llsc x2, x2, x4", "nop"
alt_lse " stlxr w5, x2, [x1]", "nop"
alt_lse " cbnz w5, 1b", "nop"
alt_lse " dmb ish", "nop"
and x0, x0, #1
3: ret
ret
ENDPROC(\name )
.endm
/*
* Atomic bit operations.
*/
bitop change_bit, eor
bitop clear_bit, bic
bitop set_bit, orr
bitop change_bit, eor, steor
bitop clear_bit, bic, stclr
bitop set_bit, orr, stset
testop test_and_change_bit, eor
testop test_and_clear_bit, bic
testop test_and_set_bit, orr
testop test_and_change_bit, eor, ldeoral
testop test_and_clear_bit, bic, ldclral
testop test_and_set_bit, orr, ldsetal