[PATCH v3 1/2] arm_arch_timer: Expose event stream status

[Suzuki K Poulose]

On 29/09/17 11:52, Julien Thierry wrote:
> The arch timer configuration for a CPU might get reset after suspending
> said CPU.
> 
> In order to reliably use the event stream in the kernel (e.g. for delays),
> we keep track of the state where we can safely concider the event stream as

nit: consider

> properly configured.
> 
> Signed-off-by: Julien Thierry <julien.thierry at arm.com>
> Cc: Mark Rutland <mark.rutland at arm.com>
> Cc: Marc Zyngier <marc.zyngier at arm.com>
> Cc: Russell King <linux at armlinux.org.uk>
> Cc: Catalin Marinas <catalin.marinas at arm.com>
> Cc: Will Deacon <will.deacon at arm.com>
> ---
>   arch/arm/include/asm/arch_timer.h    |  1 +
>   arch/arm64/include/asm/arch_timer.h  |  1 +
>   drivers/clocksource/arm_arch_timer.c | 20 ++++++++++++++++++--
>   include/clocksource/arm_arch_timer.h |  6 ++++++
>   4 files changed, 26 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h
> index d4ebf56..0b6e104 100644
> --- a/arch/arm/include/asm/arch_timer.h
> +++ b/arch/arm/include/asm/arch_timer.h
> @@ -106,6 +106,7 @@ static inline u32 arch_timer_get_cntkctl(void)
>   static inline void arch_timer_set_cntkctl(u32 cntkctl)
>   {
>   	asm volatile("mcr p15, 0, %0, c14, c1, 0" : : "r" (cntkctl));
> +	isb();
>   }
> 
>   #endif
> diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
> index a652ce0..bdedd8f 100644
> --- a/arch/arm64/include/asm/arch_timer.h
> +++ b/arch/arm64/include/asm/arch_timer.h
> @@ -144,6 +144,7 @@ static inline u32 arch_timer_get_cntkctl(void)
>   static inline void arch_timer_set_cntkctl(u32 cntkctl)
>   {
>   	write_sysreg(cntkctl, cntkctl_el1);
> +	isb();
>   }
> 
>   static inline u64 arch_counter_get_cntpct(void)
> diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
> index fd4b7f6..47cf15e 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -77,6 +77,7 @@ struct arch_timer {
>   static bool arch_counter_suspend_stop;
>   static bool vdso_default = true;
> 
> +static cpumask_t evtstrm_available;
>   static bool evtstrm_enable = IS_ENABLED(CONFIG_ARM_ARCH_TIMER_EVTSTREAM);
> 
>   static int __init early_evtstrm_cfg(char *buf)
> @@ -740,6 +741,7 @@ static void arch_timer_evtstrm_enable(int divider)
>   #ifdef CONFIG_COMPAT
>   	compat_elf_hwcap |= COMPAT_HWCAP_EVTSTRM;
>   #endif
> +	cpumask_set_cpu(smp_processor_id(), &evtstrm_available);
>   }
> 
>   static void arch_timer_configure_evtstream(void)
> @@ -864,6 +866,11 @@ u32 arch_timer_get_rate(void)
>   	return arch_timer_rate;
>   }
> 
> +bool arch_timer_evtstrm_available(void)
> +{
> +	return !!cpumask_test_cpu(smp_processor_id(), &evtstrm_available);
> +}
> +

This could live in the header file as static inlin, if the evtstrm_available
is made global and could avoid a function call where it is used.

Suzuki