Re: [PATCH] ARM: add cpu_idle_wait() to support CPUidle on SMP systems.

[Kevin Hilman <khilman@deeprootsystems.com>]

Russell,

Kevin Hilman <khilman@deeprootsystems.com> writes:

> In order for CPUidle to work on SMP systems, an implementation of
> cpu_idle_wait() is needed.
>
> This patch duplicates the x86 implementation of cpu_idle_wait() for
> ARM.
>
> Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>

Are you OK with this for the patch system for 2.6.37?

Kevin

> ---
>  arch/arm/Kconfig              |    3 +++
>  arch/arm/include/asm/system.h |    2 ++
>  arch/arm/kernel/process.c     |   19 +++++++++++++++++++
>  3 files changed, 24 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 553b7cf..10ce6dc 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -145,6 +145,9 @@ config ARCH_HAS_CPUFREQ
>  	  and that the relevant menu configurations are displayed for
>  	  it.
>  
> +config ARCH_HAS_CPU_IDLE_WAIT
> +       def_bool y
> +
>  config GENERIC_HWEIGHT
>  	bool
>  	default y
> diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h
> index 8ba1ccf..48e360c 100644
> --- a/arch/arm/include/asm/system.h
> +++ b/arch/arm/include/asm/system.h
> @@ -325,6 +325,8 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size
>  extern void disable_hlt(void);
>  extern void enable_hlt(void);
>  
> +void cpu_idle_wait(void);
> +
>  #include <asm-generic/cmpxchg-local.h>
>  
>  #if __LINUX_ARM_ARCH__ < 6
> diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
> index 401e38b..23def52 100644
> --- a/arch/arm/kernel/process.c
> +++ b/arch/arm/kernel/process.c
> @@ -135,6 +135,25 @@ EXPORT_SYMBOL(pm_power_off);
>  void (*arm_pm_restart)(char str, const char *cmd) = arm_machine_restart;
>  EXPORT_SYMBOL_GPL(arm_pm_restart);
>  
> +static void do_nothing(void *unused)
> +{
> +}
> +
> +/*
> + * cpu_idle_wait - Used to ensure that all the CPUs discard old value of
> + * pm_idle and update to new pm_idle value. Required while changing pm_idle
> + * handler on SMP systems.
> + *
> + * Caller must have changed pm_idle to the new value before the call. Old
> + * pm_idle value will not be used by any CPU after the return of this function.
> + */
> +void cpu_idle_wait(void)
> +{
> +	smp_mb();
> +	/* kick all the CPUs so that they exit out of pm_idle */
> +	smp_call_function(do_nothing, NULL, 1);
> +}
> +EXPORT_SYMBOL_GPL(cpu_idle_wait);
>  
>  /*
>   * This is our default idle handler.  We need to disable