linux-kernel - Re: [PATCH v2 4/6] clocksource: Change CPU hotplug priority of exynos

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Date:   Tue, 16 Oct 2018 09:59:22 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-samsung-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <marc.zyngier@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Inki Dae <inki.dae@...sung.com>
Subject: Re: [PATCH v2 4/6] clocksource: Change CPU hotplug priority of
 exynos_mct driver

On 2018년 10월 15일 21:31, Marek Szyprowski wrote:
> Exynos Multi-Core Timer driver (exynos_mct) must be started before
> ARM Architected Timers (arch_timer), because both timers share common
> hardware block and turning on MCT is needed to get ARM Architected
> Timer working properly.
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> Acked-by: Krzysztof Kozlowski <krzk@...nel.org>
> ---
>  include/linux/cpuhotplug.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index caf40ad0bbc6..5d9e4a6ea299 100644
> --- a/include/linux/cpuhotplug.h
> +++ b/include/linux/cpuhotplug.h
> @@ -115,10 +115,10 @@ enum cpuhp_state {
>  	CPUHP_AP_PERF_ARM_ACPI_STARTING,
>  	CPUHP_AP_PERF_ARM_STARTING,
>  	CPUHP_AP_ARM_L2X0_STARTING,
> +	CPUHP_AP_EXYNOS4_MCT_TIMER_STARTING,
>  	CPUHP_AP_ARM_ARCH_TIMER_STARTING,
>  	CPUHP_AP_ARM_GLOBAL_TIMER_STARTING,
>  	CPUHP_AP_JCORE_TIMER_STARTING,
> -	CPUHP_AP_EXYNOS4_MCT_TIMER_STARTING,
>  	CPUHP_AP_ARM_TWD_STARTING,
>  	CPUHP_AP_QCOM_TIMER_STARTING,
>  	CPUHP_AP_ARMADA_TIMER_STARTING,
> 

On Exynos SoC, ARM architecture timer shares the block of Exynos MCT timer.
For using arch_timer, Exynos MCT timer should be initialized before arch_timer.
I agree about this.

Reviewed-by: Chanwoo Choi <cw00.choi@...sung.com>

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics