linux-kernel - Re: [PATCH v2 6/7] ARM: EXYNOS: PM: fix register setup on EXYNOS4x12 for AFTR mode code

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Date:	Mon, 02 Jun 2014 15:10:05 +0200
From:	Tomasz Figa <tomasz.figa@...il.com>
To:	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Kukjin Kim <kgene.kim@...sung.com>
CC:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Tomasz Figa <t.figa@...sung.com>,
	Sachin Kamat <sachin.kamat@...aro.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	linux-samsung-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH v2 6/7] ARM: EXYNOS: PM: fix register setup on EXYNOS4x12
 for AFTR mode code

Hi,

On 02.06.2014 14:35, Bartlomiej Zolnierkiewicz wrote:
> Add S5P_CENTRAL_SEQ_OPTION register setup for EXYNOS4x12 to AFTR
> mode code.  Without this setup AFTR mode doesn't show any benefit
> over WFI one.  When this setup is applied AFTR mode reduces power
> consumption by ~12% (as measured on Trats2 board).
> 
> This change is a preparation for adding secure firmware support to
> EXYNOS cpuidle driver.
> 
> Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
> Acked-by: Kyungmin Park <kyungmin.park@...sung.com>
> ---
>  arch/arm/mach-exynos/pm.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/arm/mach-exynos/pm.c b/arch/arm/mach-exynos/pm.c
> index aeff99e..0fb9a5a 100644
> --- a/arch/arm/mach-exynos/pm.c
> +++ b/arch/arm/mach-exynos/pm.c
> @@ -456,6 +456,10 @@ static int exynos_cpu_pm_notifier(struct notifier_block *self,
>  	case CPU_PM_ENTER:
>  		if (cpu == 0) {
>  			exynos_pm_central_suspend();
> +			if (soc_is_exynos4212() || soc_is_exynos4412())
> +				__raw_writel(S5P_USE_STANDBY_WFI0 |
> +					     S5P_USE_STANDBY_WFE0,
> +					     S5P_CENTRAL_SEQ_OPTION);

I wonder whether this isn't required on any Exynos SoC in general, as
this mask decides which STANDBY_WFI/WFE signals are considered before
entering the lower power state.

Also you should check the behavior with Krzysztof's patch adding support
for delayed reset assertion, which should cause WFI/WFE signals of CPUs
powered down to be kept asserted.

Best regards,
Tomasz
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