[PATCH 2/2] efi/arm64: use UEFI for system reset

[Catalin Marinas]

On Fri, Aug 29, 2014 at 04:05:57PM +0100, Ard Biesheuvel wrote:
> If UEFI Runtime Services are available, they are preferred over direct
> PSCI calls or other methods to reset the system.
> 
> For the reset case, we need to hook into machine_restart(), as the
> arm_pm_restart function pointer may be overwritten by modules.
> 
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> ---
>  arch/arm64/kernel/process.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index 1309d64aa926..335a93da5eeb 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -177,6 +177,13 @@ void machine_restart(char *cmd)
>  	local_irq_disable();
>  	smp_send_stop();
>  
> +	/*
> +	 * arm_pm_restart is exported to modules, so the only way to supersede
> +	 * it with efi_reboot() is to call it here.
> +	 */

Why do you make this the preferred method? Is there a risk that UEFI is
broken and we want to override it with a SoC-specific driver (I wouldn't
like it but it's still an option).

There are also some patches here that try to get rid of arm_pm_restart:

https://lkml.org/lkml/2014/8/19/665

Once there are no drivers for arm64 setting arm_pm_restart explicitly
I'll remove it.

> +	if (IS_ENABLED(CONFIG_EFI) && efi_enabled(EFI_RUNTIME_SERVICES))

efi_enabled always returns false if !IS_ENABLED(CONFIG_EFI).

> +		efi_reboot(REBOOT_WARM, NULL);
> +
>  	/* Now call the architecture specific reboot code. */
>  	if (arm_pm_restart)
>  		arm_pm_restart(reboot_mode, cmd);
> -- 
> 1.8.3.2
> 
> 

-- 
Catalin