linux-kernel - Re: [RFC PATCH 2/7] arm64: kernel: Add a WFI hook.

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Date:   Thu, 21 Jan 2021 11:52:13 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     Mohamed Mediouni <mohamed.mediouni@...amail.com>
Cc:     Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Hector Martin <marcan@...can.st>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
        Stan Skowronek <stan@...ellium.com>
Subject: Re: [RFC PATCH 2/7] arm64: kernel: Add a WFI hook.

On Wed, Jan 20, 2021 at 2:27 PM Mohamed Mediouni
<mohamed.mediouni@...amail.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