linux-kernel - Re: [PATCH 2/2] ARM: vf610: Use ARM Global Timer as clocksource

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Date:	Thu, 25 Sep 2014 15:50:15 +0800
From:	Shawn Guo <shawn.guo@...escale.com>
To:	Stefan Agner <stefan@...er.ch>
CC:	<kernel@...gutronix.de>, <festevam@...il.com>,
	<jingchang.lu@...escale.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] ARM: vf610: Use ARM Global Timer as clocksource

On Thu, Sep 11, 2014 at 02:06:15PM +0200, Stefan Agner wrote:
> Use ARM Global Timer as clocksource instead of the PIT timer. This
> leaves the PIT timer for other users e.g. the secondary Cortex-M4
> core. Also, the Global Timer has double the precission (running at
> pheripheral clock compared to IPG clock) and a 64-bit incrementing
> counter register.

I just think of one thing.  Will this change cause a problem of the low
power idle support in case we want to power down ARM core in there?

Shawn

> 
> Signed-off-by: Stefan Agner <stefan@...er.ch>
> ---
> Theoretically we could remove the PIT driver now. But we could also
> enable both drivers, but is having two clock source useful for the
> Kernel at all?
> 
>  arch/arm/mach-imx/Kconfig | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mach-imx/Kconfig b/arch/arm/mach-imx/Kconfig
> index 64161aa..adc77180 100644
> --- a/arch/arm/mach-imx/Kconfig
> +++ b/arch/arm/mach-imx/Kconfig
> @@ -656,7 +656,8 @@ config SOC_VF610
>  	bool "Vybrid Family VF610 support"
>  	select ARM_GIC
>  	select PINCTRL_VF610
> -	select VF_PIT_TIMER
> +	select ARM_GLOBAL_TIMER
> +	select CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
>  	select PL310_ERRATA_769419 if CACHE_L2X0
>  
>  	help
> -- 
> 2.1.0
> 
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