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

[Mohamed Mediouni]

> On 21 Jan 2021, at 11:52, Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
> 
> On Wed, Jan 20, 2021 at 2:27 PM Mohamed Mediouni
> <mohamed.mediouni@xxxxxxxxxxxx> 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.
Can we make sure that wfi never gets called even on early
boot when using a cpuidle driver?

Thank you,
> 
>       Arnd