linux-kernel - Re: [PATCH v6 2/3] ARM: rockchip: ensure CPU to enter WFI/WFE state

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Date:	Wed, 10 Jun 2015 13:59:16 +0800
From:	Kever Yang <kever.yang@...k-chips.com>
To:	Caesar Wang <wxt@...k-chips.com>, Heiko Stuebner <heiko@...ech.de>
CC:	Russell King <linux@....linux.org.uk>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	dianders@...omium.org, linux-kernel@...r.kernel.org,
	linux-rockchip@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v6 2/3] ARM: rockchip: ensure CPU to enter WFI/WFE state

Hi Caesar,

On 06/09/2015 05:49 PM, Caesar Wang wrote:
> The patch can ensure that v7_exit_coherency_flush() in rockchip_cpu_die()
> executed in time.
> The mdelay(1) has enough time to fix the problem of CPU offlining.
> That's a workaround way in rockchip hotplug code,
> At least, we haven't a better way to solve it. Who know,
> that maybe fixed by chip (hardware) in the future.
>
> Signed-off-by: Caesar Wang <wxt@...k-chips.com>
>
> ---
>
> Changes in v6:
> - Fix the delay 1ms describing.
> Series-changes: 5
> - Fix the patch decription.
> - Add the changelog.
> Series-changes: 2
> - As Kever points out, Fix the subject typo WFI/WFE.
>
>   arch/arm/mach-rockchip/platsmp.c | 7 +++++++
>   1 file changed, 7 insertions(+)
>
> diff --git a/arch/arm/mach-rockchip/platsmp.c b/arch/arm/mach-rockchip/platsmp.c
> index b379cc8..d629206 100644
> --- a/arch/arm/mach-rockchip/platsmp.c
> +++ b/arch/arm/mach-rockchip/platsmp.c
> @@ -322,6 +322,13 @@ static void __init rockchip_smp_prepare_cpus(unsigned int max_cpus)
>   #ifdef CONFIG_HOTPLUG_CPU
>   static int rockchip_cpu_kill(unsigned int cpu)
>   {
> +	/*
> +	 * We need a delay here to ensure that the dying CPU can finish
> +	 * executing v7_coherency_exit() and reach the WFI/WFE state
> +	 * prior to having the power domain disabled.
> +	 */
> +	mdelay(1);
> +
>   	pmu_set_power_domain(0 + cpu, false);
>   	return 1;
>   }
Reviewed-by: Kever Yang <kever.yang@...k-chips.com>

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