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References: <20210120132717.395873-1-mohamed.mediouni@caramail.com> <20210120132717.395873-3-mohamed.mediouni@caramail.com>
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From:   Arnd Bergmann <arnd@kernel.org>
Date:   Thu, 21 Jan 2021 11:52:13 +0100
Message-ID: <CAK8P3a20XRHaErO5445ds6tf0omSKLMZ_NAWdS=9nBbLb7rdvg@mail.gmail.com>
Subject: Re: [RFC PATCH 2/7] arm64: kernel: Add a WFI hook.
To:     Mohamed Mediouni <mohamed.mediouni@caramail.com>
Cc:     Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Hector Martin <marcan@marcan.st>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>,
        Stan Skowronek <stan@corellium.com>
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On Wed, Jan 20, 2021 at 2:27 PM Mohamed Mediouni
<mohamed.mediouni@caramail.com> wrote:
> --- a/arch/arm64/kernel/cpu_ops.c
> +++ b/arch/arm64/kernel/cpu_ops.c

>  #if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_STACKPROTECTOR_PER_TASK)
>  #include <linux/stackprotector.h>
> @@ -74,8 +75,14 @@ void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);
>
>  static void noinstr __cpu_do_idle(void)
>  {
> -       dsb(sy);
> -       wfi();
> +       const struct cpu_operations *ops = get_cpu_ops(task_cpu(current));
> +
> +       if (ops->cpu_wfi) {
> +               ops->cpu_wfi();
> +       } else {
> +               dsb(sy);
> +               wfi();
> +       }
>  }

I think the correct place to put this would be a platform specific driver
in drivers/cpuidle/ instead of an added low-level callback in the
default idle function and a custom cpu_operations structure.

       Arnd