linux-kernel - Re: [PATCH] arm64: support reboot and power off via EFI runtime

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Message-ID: <20140618132623.GF26461@leverpostej>
Date:	Wed, 18 Jun 2014 14:26:23 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	"msalter@...hat.com" <msalter@...hat.com>
Cc:	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] arm64: support reboot and power off via EFI runtime

Hi Mark,

On Tue, Jun 17, 2014 at 05:45:14PM +0100, Mark Salter wrote:
> Add handlers for arm_pm_resestart and pm_power_off which use EFI
> runtime services ResetSystem call to perform the functions. These
> handlers are only installed if no handler currently exists. This
> allows PSCI to take priority over EFI for these functions.
> 
> Signed-off-by: Mark Salter <msalter@...hat.com>
> ---
>  arch/arm64/kernel/efi.c | 40 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)
> 
> diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
> index 14db1f6..e8c0476 100644
> --- a/arch/arm64/kernel/efi.c
> +++ b/arch/arm64/kernel/efi.c
> @@ -19,11 +19,14 @@
>  #include <linux/of_fdt.h>
>  #include <linux/sched.h>
>  #include <linux/slab.h>
> +#include <linux/reboot.h>
> +#include <linux/pm.h>
>  
>  #include <asm/cacheflush.h>
>  #include <asm/efi.h>
>  #include <asm/tlbflush.h>
>  #include <asm/mmu_context.h>
> +#include <asm/system_misc.h>
>  
>  struct efi_memory_map memmap;
>  
> @@ -467,3 +470,40 @@ static int __init arm64_enter_virtual_mode(void)
>  	return 0;
>  }
>  early_initcall(arm64_enter_virtual_mode);
> +
> +static void efi_restart(enum reboot_mode reboot_mode, const char *cmd)
> +{
> +	int efi_mode;
> +
> +	switch (reboot_mode) {
> +	case REBOOT_WARM:
> +	case REBOOT_SOFT:
> +		efi_mode = EFI_RESET_WARM;
> +		break;
> +	default:
> +		efi_mode = EFI_RESET_COLD;
> +		break;
> +	}
> +	efi.reset_system(efi_mode, 0, 0, NULL);
> +}
> +
> +static void efi_power_off(void)
> +{
> +	efi.reset_system(EFI_RESET_SHUTDOWN, 0, 0, NULL);
> +}
> +
> +static int __init setup_efi_reset(void)
> +{
> +	if (efi_enabled(EFI_RUNTIME_SERVICES)) {
> +		/*
> +		 * If something (psci, etc) hasn't already registered
> +		 * a handler, use EFI.
> +		 */
> +		if (arm_pm_restart == NULL)
> +			arm_pm_restart = efi_restart;
> +		if (pm_power_off == NULL)
> +			pm_power_off = efi_power_off;
> +	}
> +	return 0;
> +}
> +pure_initcall(setup_efi_reset);

This doesn't seem to match the definition of a pure initcall, given that
it depends on the state of EFI runtime services and
arm_{pm_restart,power_off}.

Is there any reason this needs to run so early? Can this not be
called later, when we have more of a guarantee of other reboot /
shutdown mechanisms having been registered?

Cheers,
Mark.
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