Messages in this thread | | | Date | Thu, 12 Sep 2013 12:24:52 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH 3/4] Add physical count arch timer support for clocksource in ARMv7. |
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On Thu, Sep 12, 2013 at 07:51:26AM +0100, Fan Rong wrote: > Signed-off-by: Fan Rong <cinifr@gmail.com> > --- > arch/arm/include/asm/arch_timer.h | 11 +++++++++++ > drivers/clocksource/Kconfig | 8 ++++++++ > drivers/clocksource/arm_arch_timer.c | 10 +++++++++- > 3 files changed, 28 insertions(+), 1 deletion(-) > > diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h > index 5665134..24c904a 100644 > --- a/arch/arm/include/asm/arch_timer.h > +++ b/arch/arm/include/asm/arch_timer.h > @@ -87,6 +87,17 @@ static inline u64 arch_counter_get_cntvct(void) > return cval; > } > > +static inline u64 arch_counter_get_cntpct(void) > +{ > + u64 cval; > + > + isb(); > + asm volatile("mrrc p15, 0, %Q0, %R0, c14" : "=r" (cval)); > + return cval; > +} > + > + > + > static inline void arch_counter_set_user_access(void) > { > u32 cntkctl; > diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig > index 41c6946..a4981d2 100644 > --- a/drivers/clocksource/Kconfig > +++ b/drivers/clocksource/Kconfig > @@ -109,3 +109,11 @@ config VF_PIT_TIMER > bool > help > Support for Period Interrupt Timer on Freescale Vybrid Family SoCs. > +menu "Clock Source" > + > +config ARM_ARCH_TIMER_USE_PHYCNT > + bool "Use Physical Count Timer" > + depends on ARM_ARCH_TIMER > + help > + If bootloader dont set Virtual Offset register,Physical Count Timer is needed to replace Virtual Count Timer. > +endmenu
This cannot be a compile-time option as above in a multiplatform build. Other paltforms (e.g. KVM guests) *must* use the virtual counters to get any semblance of a consistent view of time.
Why can the bootloader not be fixed to set CNTVOFF (or to boot the kernel in Hyp mode)?
Thanks, Mark.
> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c > index fbd9ccd..884e4d1 100644 > --- a/drivers/clocksource/arm_arch_timer.c > +++ b/drivers/clocksource/arm_arch_timer.c > @@ -372,7 +372,11 @@ static u64 arch_counter_get_cntvct_mem(void) > * to exist on arm64. arm doesn't use this before DT is probed so even > * if we don't have the cp15 accessors we won't have a problem. > */ > -u64 (*arch_timer_read_counter)(void) = arch_counter_get_cntvct; > +#ifdef CONFIG_ARM_ARCH_TIMER_USE_PHYCNT > + u64 (*arch_timer_read_counter)(void) = arch_counter_get_cntpct; > +#else > + u64 (*arch_timer_read_counter)(void) = arch_counter_get_cntvct; > +#endif > > static cycle_t arch_counter_read(struct clocksource *cs) > { > @@ -410,7 +414,11 @@ static void __init arch_counter_register(unsigned type) > > /* Register the CP15 based counter if we have one */ > if (type & ARCH_CP15_TIMER) > +#ifdef CONFIG_ARM_ARCH_TIMER_USE_PHYCNT > + arch_timer_read_counter = arch_counter_get_cntpct; > +#else > arch_timer_read_counter = arch_counter_get_cntvct; > +#endif > else > arch_timer_read_counter = arch_counter_get_cntvct_mem; > > -- > 1.7.9.5 > >
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