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

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Date:	Tue, 29 Jul 2014 21:00:51 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	Sudeep Holla <sudeep.holla@....com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Mark Rutland <Mark.Rutland@....com>
CC:	"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 2014-7-29 2:28, Sudeep Holla wrote:
> 
> 
> 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.

I think it will not be executed, since ARM64 do not support S1 and S3 in ACPI
for now, and that state will not defined, then acpi_suspend_enter will not be
called.

Thanks
Hanjun

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