Re: [PATCH] ACPI: processor: Add cpuidle driver check in acpi_processor_register_idle_driver

["lihuisong (C)" <lihuisong@huawei.com>]

On 6/8/2026 2:38 PM, Tony W Wang-oc wrote:
> Commit 7a8c994cbb2d ("ACPI: processor: idle: Optimize ACPI idle
> driver registration") moved the ACPI idle driver registration to
> acpi_processor_driver_init(), but it didn't check whether a cpuidle
> driver was already registered.
>
> For example, on Intel platforms, if the intel_idle driver is already
> loaded, the code would still evaluate the _CST object in the ACPI
> table and attempt to register the acpi_idle driver. This registration
> would fail with -EBUSY due to the existing check in cpuidle_register_driver.
>
> Add a check at the beginning of acpi_processor_register_idle_driver()
> to avoid unnecessary _CST evaluate and potential registration failures.
Now look good to me. Thanks.
> Fixes: 7a8c994cbb2d ("ACPI: processor: idle: Optimize ACPI idle driver registration")
> Signed-off-by: Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>
> ---
>   drivers/acpi/processor_idle.c | 5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index ee5facccbe10..0409411abb83 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -1355,6 +1355,11 @@ void acpi_processor_register_idle_driver(void)
>   	int ret = -ENODEV;
>   	int cpu;
>   
Can you add some like below comment?
"No need to register the ACPI idle driver when platform don't use this 
driver."
> +	if (cpuidle_get_driver()) {
> +		pr_debug("cpuidle driver %pS already registered.\n", cpuidle_get_driver());
> +		return;
> +	}
> +
>   	acpi_processor_update_max_cstate();
>   
>   	/*