linux-kernel - Re: [PATCH 03/19] ARM64 / ACPI: Introduce lowlevel suspend function

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Message-ID: <53D69665.5090709@arm.com>
Date:	Mon, 28 Jul 2014 19:28:53 +0100
From:	Sudeep Holla <sudeep.holla@....com>
To:	Hanjun Guo <hanjun.guo@...aro.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Mark Rutland <Mark.Rutland@....com>
CC:	Sudeep Holla <sudeep.holla@....com>,
	"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Will Deacon <Will.Deacon@....com>,
	Jason Cooper <jason@...edaemon.net>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Mark Brown <broonie@...aro.org>,
	Robert Richter <rric@...nel.org>,
	Lv Zheng <lv.zheng@...el.com>,
	Robert Moore <robert.moore@...el.com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Liviu Dudau <Liviu.Dudau@....com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Charles Garcia-Tobin <Charles.Garcia-Tobin@....com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/19] ARM64 / ACPI: Introduce lowlevel suspend function



On 24/07/14 14:00, Hanjun Guo wrote:
> From: Graeme Gregory <graeme.gregory@...aro.org>
>
> acpi_wakeup_address is used on x86 as the address bios jumps into
> when machine wakes up from suspend. As arm64 does not have such a
> bios this mechanism will be provided by other means. But the define
> is still required inside the acpi core.
>
> Introduce a null stub for acpi_suspend_lowlevel as this is also
> required by core. This will be filled in when standards are
> defined for arm64 ACPI global power states.
>
> Reviewed-by: Grant Likely <grant.likely@...aro.org>
> Signed-off-by: Graeme Gregory <graeme.gregory@...aro.org>
> Signed-off-by: Hanjun Guo <hanjun.guo@...aro.org>
> ---
>   arch/arm64/include/asm/acpi.h |   12 ++++++++++++
>   arch/arm64/kernel/acpi.c      |    7 +++++++
>   2 files changed, 19 insertions(+)
>
> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
> index e8581ea..44b617f 100644
> --- a/arch/arm64/include/asm/acpi.h
> +++ b/arch/arm64/include/asm/acpi.h
> @@ -36,6 +36,18 @@ static inline bool acpi_has_cpu_in_madt(void)
>   	return 1;
>   }
>
> +/* Low-level suspend routine.
> + *
> + * ACPI S-states for ARM64 have to be defined
> + * and approved before doing anything else, maybe
> + * we need update the ACPI spec, here we
> + * just introduce function and macro needed by
> + * ACPI core as IA64 did, and revisit them when
> + * the spec is ready.
> + */
> +extern int (*acpi_suspend_lowlevel)(void);
> +#define acpi_wakeup_address 0
> +

While I understand that this is temporary solution, but will this be
sufficient to make sure we don't enter acpi_suspend_enter ?

A brief look at acpi_suspend_enter showed access to write to
ACPI_BITREG_SCI_ENABLE which might just explode. But if you are sure that
it will not be executed, then it should be fine for now.

Regards,
Sudeep


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