From mboxrd@z Thu Jan  1 00:00:00 1970
From: will.deacon@arm.com (Will Deacon)
Date: Mon, 21 Jul 2014 09:51:50 +0100
Subject: [PATCH 2/3] ARM: smp_scu: enable SCU standby support
In-Reply-To: <1405928755-19413-3-git-send-email-shawn.guo@freescale.com>
References: <1405928755-19413-1-git-send-email-shawn.guo@freescale.com>
 <1405928755-19413-3-git-send-email-shawn.guo@freescale.com>
Message-ID: <20140721085150.GB15666@arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Mon, Jul 21, 2014 at 08:45:54AM +0100, Shawn Guo wrote:
> With SCU standby enabled, SCU CLK will be turned off when all processors
> are in WFI mode.  And the clock will be turned on when any processor
> leaves WFI mode.
> 
> This behavior should be preferable in terms of power efficiency of
> system idle.  So let's set the SCU standby bit to enable the support in
> function scu_enable().
> 
> Signed-off-by: Shawn Guo <shawn.guo@freescale.com>
> ---
>  arch/arm/kernel/smp_scu.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/kernel/smp_scu.c b/arch/arm/kernel/smp_scu.c
> index c947508f84e6..9f29d167d02c 100644
> --- a/arch/arm/kernel/smp_scu.c
> +++ b/arch/arm/kernel/smp_scu.c
> @@ -18,6 +18,7 @@
>  
>  #define SCU_CTRL		0x00
>  #define SCU_ENABLE		(1 << 0)
> +#define SCU_STANDBY_ENABLE	(1 << 5)
>  #define SCU_CONFIG		0x04
>  #define SCU_CPU_STATUS		0x08
>  #define SCU_INVALIDATE		0x0c
> @@ -54,7 +55,7 @@ void scu_enable(void __iomem *scu_base)
>  	if (scu_ctrl & SCU_ENABLE)
>  		return;
>  
> -	scu_ctrl |= SCU_ENABLE;
> +	scu_ctrl |= SCU_ENABLE | SCU_STANDBY_ENABLE;

I don't think this bit exists on all revisions of the A9.

Will