diff options
| author | Joey Gouly <joey.gouly@arm.com> | 2022-08-30 11:48:33 +0100 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2022-09-09 12:27:25 +0100 |
| commit | 9025cebf12d1763de36d5e09e2b0a1e4f9b13b28 (patch) | |
| tree | a09684f0d2d76fce16058feab394db7fcca90453 /arch/arm64/include/asm/vdso | |
| parent | 4e3bca8f7cdd3b658ee7ad700fdce95b5e13a441 (diff) | |
arm64: vdso: use SYS_CNTVCTSS_EL0 for gettimeofday
If FEAT_ECV is implemented, the self-synchronized counter CNTVCTSS_EL0 can
be used, removing the need for an ISB.
Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andre Przywara <andre.przywara@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20220830104833.34636-4-joey.gouly@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/include/asm/vdso')
| -rw-r--r-- | arch/arm64/include/asm/vdso/gettimeofday.h | 19 |
1 files changed, 15 insertions, 4 deletions
diff --git a/arch/arm64/include/asm/vdso/gettimeofday.h b/arch/arm64/include/asm/vdso/gettimeofday.h index 4f7a629df81f..764d13e2916c 100644 --- a/arch/arm64/include/asm/vdso/gettimeofday.h +++ b/arch/arm64/include/asm/vdso/gettimeofday.h @@ -7,8 +7,10 @@ #ifndef __ASSEMBLY__ +#include <asm/alternative.h> #include <asm/barrier.h> #include <asm/unistd.h> +#include <asm/sysreg.h> #define VDSO_HAS_CLOCK_GETRES 1 @@ -78,11 +80,20 @@ static __always_inline u64 __arch_get_hw_counter(s32 clock_mode, return 0; /* - * This isb() is required to prevent that the counter value + * If FEAT_ECV is available, use the self-synchronizing counter. + * Otherwise the isb is required to prevent that the counter value * is speculated. - */ - isb(); - asm volatile("mrs %0, cntvct_el0" : "=r" (res) :: "memory"); + */ + asm volatile( + ALTERNATIVE("isb\n" + "mrs %0, cntvct_el0", + "nop\n" + __mrs_s("%0", SYS_CNTVCTSS_EL0), + ARM64_HAS_ECV) + : "=r" (res) + : + : "memory"); + arch_counter_enforce_ordering(res); return res; |