linux-kernel - Re: [PATCH v2 3/3] ARM: vf610: Add ARM Global Timer clocksource option

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Date:	Mon, 29 Sep 2014 19:51:41 +0800
From:	Shawn Guo <shawn.guo@...escale.com>
To:	Stefan Agner <stefan@...er.ch>
CC:	<kernel@...gutronix.de>, <daniel.lezcano@...aro.org>,
	<tglx@...utronix.de>, <festevam@...il.com>,
	<jingchang.lu@...escale.com>, <bpringlemeir@...ps.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/3] ARM: vf610: Add ARM Global Timer clocksource
 option

On Wed, Sep 24, 2014 at 06:20:10PM +0200, Stefan Agner wrote:
> Add the ARM Global Timer as clocksource/scheduler clock option and
> use it as default scheduler clock. 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. We still keep
> the PIT timer as an secondary option in case the ARM Global Timer is
> not available.
> 
> Signed-off-by: Stefan Agner <stefan@...er.ch>
> ---
>  arch/arm/mach-imx/Kconfig | 19 ++++++++++++++++++-
>  1 file changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mach-imx/Kconfig b/arch/arm/mach-imx/Kconfig
> index 11b2957..9482f58 100644
> --- a/arch/arm/mach-imx/Kconfig
> +++ b/arch/arm/mach-imx/Kconfig
> @@ -633,12 +633,29 @@ config SOC_VF610
>  	bool "Vybrid Family VF610 support"
>  	select ARM_GIC
>  	select PINCTRL_VF610
> -	select VF_PIT_TIMER
>  	select PL310_ERRATA_769419 if CACHE_L2X0
>  
>  	help
>  	  This enable support for Freescale Vybrid VF610 processor.
>  
> +choice
> +	prompt "Clocksource for scheduler clock"
> +	depends on SOC_VF610
> +	default ARM_GLOBAL_TIMER
> +
> +	config ARM_GLOBAL_TIMER
> +		bool "Use ARM Global Timer"
> +		select CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
> +		help
> +		  Use the ARM Global Timer as clocksource
> +
> +	config VF_PIT_TIMER
> +		bool "Use PIT timer"
> +		help
> +		  Use SoC Periodic Interrupt Timer (PIT) as clocksource
> +
> +endchoice
> +

As per the report from 0-DAY kernel build test (thanks), the change
causes the following warning on a particular config.

warning: (ARCH_ROCKCHIP && ARCH_BCM_5301X) selects CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK which has unmet direct dependencies (ARM_GLOBAL_TIMER)

It looks the redefinition of ARM_GLOBAL_TIMER is the cause for that
warning.  I think it's more safer to use new config symbols for choosing
the clocksource device for VF610.  I propose the following change to fix
the warning.  If there is no objection, I will squash it into the
original commit soon.

diff --git a/arch/arm/mach-imx/Kconfig b/arch/arm/mach-imx/Kconfig
index 9482f5837b7e..e26b0fdd72db 100644
--- a/arch/arm/mach-imx/Kconfig
+++ b/arch/arm/mach-imx/Kconfig
@@ -641,16 +641,18 @@ config SOC_VF610
 choice
        prompt "Clocksource for scheduler clock"
        depends on SOC_VF610
-       default ARM_GLOBAL_TIMER
+       default VF_USE_ARM_GLOBAL_TIMER
 
-       config ARM_GLOBAL_TIMER
+       config VF_USE_ARM_GLOBAL_TIMER
                bool "Use ARM Global Timer"
+               select ARM_GLOBAL_TIMER
                select CLKSRC_ARM_GLOBAL_TIMER_SCHED_CLOCK
                help
                  Use the ARM Global Timer as clocksource
 
-       config VF_PIT_TIMER
+       config VF_USE_PIT_TIMER
                bool "Use PIT timer"
+               select VF_PIT_TIMER
                help
                  Use SoC Periodic Interrupt Timer (PIT) as clocksource
 

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