diff options
| author | Marc Zyngier <maz@kernel.org> | 2021-10-17 13:42:23 +0100 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2021-10-19 10:56:20 +0100 |
| commit | 9ee840a96042cef9f7d36337ce05144d6c013858 (patch) | |
| tree | 26cd3150704d6868e2bd19a493eacbfc2d0f0e11 /arch/arm64/include/asm/arch_timer.h | |
| parent | fdf865988b5a404f91f86a1b3b665440a9ebafb2 (diff) | |
arm64: Add CNT{P,V}CTSS_EL0 alternatives to cnt{p,v}ct_el0
CNTPCTSS_EL0 and CNTVCTSS_EL0 are alternatives to the usual
CNTPCT_EL0 and CNTVCT_EL0 that do not require a previous ISB
to be synchronised (SS stands for Self-Synchronising).
Use the ARM64_HAS_ECV capability to control alternative sequences
that switch to these low(er)-cost primitives. Note that the
counter access in the VDSO is for now left alone until we decide
whether we want to allow this.
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211017124225.3018098-16-maz@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch/arm64/include/asm/arch_timer.h')
| -rw-r--r-- | arch/arm64/include/asm/arch_timer.h | 32 |
1 files changed, 24 insertions, 8 deletions
diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h index 519ac1f7f859..af1fafbe7e1d 100644 --- a/arch/arm64/include/asm/arch_timer.h +++ b/arch/arm64/include/asm/arch_timer.h @@ -64,14 +64,26 @@ DECLARE_PER_CPU(const struct arch_timer_erratum_workaround *, static inline notrace u64 arch_timer_read_cntpct_el0(void) { - isb(); - return read_sysreg(cntpct_el0); + u64 cnt; + + asm volatile(ALTERNATIVE("isb\n mrs %0, cntpct_el0", + "nop\n" __mrs_s("%0", SYS_CNTPCTSS_EL0), + ARM64_HAS_ECV) + : "=r" (cnt)); + + return cnt; } static inline notrace u64 arch_timer_read_cntvct_el0(void) { - isb(); - return read_sysreg(cntvct_el0); + u64 cnt; + + asm volatile(ALTERNATIVE("isb\n mrs %0, cntvct_el0", + "nop\n" __mrs_s("%0", SYS_CNTVCTSS_EL0), + ARM64_HAS_ECV) + : "=r" (cnt)); + + return cnt; } #define arch_timer_reg_read_stable(reg) \ @@ -174,8 +186,10 @@ static __always_inline u64 __arch_counter_get_cntpct(void) { u64 cnt; - isb(); - cnt = read_sysreg(cntpct_el0); + asm volatile(ALTERNATIVE("isb\n mrs %0, cntpct_el0", + "nop\n" __mrs_s("%0", SYS_CNTPCTSS_EL0), + ARM64_HAS_ECV) + : "=r" (cnt)); arch_counter_enforce_ordering(cnt); return cnt; } @@ -193,8 +207,10 @@ static __always_inline u64 __arch_counter_get_cntvct(void) { u64 cnt; - isb(); - cnt = read_sysreg(cntvct_el0); + asm volatile(ALTERNATIVE("isb\n mrs %0, cntvct_el0", + "nop\n" __mrs_s("%0", SYS_CNTVCTSS_EL0), + ARM64_HAS_ECV) + : "=r" (cnt)); arch_counter_enforce_ordering(cnt); return cnt; } |