linux-kernel - Re: [update][PATCH v10 06/21] ACPI / sleep: Introduce CONFIG_ACPI_GENERIC

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Date:	Tue, 17 Mar 2015 01:59:30 -0400
From:	Jon Masters <jcm@...hat.com>
To:	Hanjun Guo <guohanjun@...wei.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	Hanjun Guo <hanjun.guo@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Olof Johansson <olof@...om.net>,
	Grant Likely <grant.likely@...aro.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Arnd Bergmann <arnd@...db.de>,
	Mark Rutland <mark.rutland@....com>,
	Graeme Gregory <graeme.gregory@...aro.org>,
	Sudeep Holla <Sudeep.Holla@....com>,
	Marc Zyngier <marc.zyngier@....com>,
	Mark Brown <broonie@...nel.org>,
	Robert Richter <rric@...nel.org>,
	Timur Tabi <timur@...eaurora.org>,
	Ashwin Chaugule <ashwinc@...eaurora.org>,
	suravee.suthikulpanit@....com, linux-acpi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linaro-acpi@...ts.linaro.org,
	Tomasz Nowicki <tomasz.nowicki@...aro.org>,
	Zhangdianfang <zhangdianfang@...wei.com>
Subject: Re: [update][PATCH v10 06/21] ACPI / sleep: Introduce CONFIG_ACPI_GENERIC_SLEEP

On 03/17/2015 12:10 AM, Hanjun Guo wrote:
> On 2015/3/17 11:23, Rafael J. Wysocki wrote:
>> On Tuesday, March 17, 2015 10:36:47 AM Hanjun Guo wrote:

>> Well, almost.  There is one problem with that, becuase sleep.c contains code
>> outside of the ACPI_SLEEP-dependent blocks.  That code is used for powering
>> off ACPI platforms.
>>
>> I guess you don't want that code on ARM too, right?
> 
> Yes, you are right.

>> Perhaps we can use ACPI_REDUCED_HARDWARE_ONLY for that?  ARM64 will be the
> 
> Sorry, I can't fully understand your intention here, could you please
> explain it more?
> 
> Let me guess a little bit. Do you mean use ACPI_REDUCED_HARDWARE_ONLY for
> powering off ACPI platforms? if so, I guess it's not a good idea, ACPI spec
> only says that S4BIOS is not supported on HW-reduced ACPI platforms, S5
> has no such limitation, if I miss something here, please let me know.

If helpful to the discussion, current SBBR (Server Base Boot
Requirements[0]) design guidance is that for power off itself, we will
prefer calling an EFI Runtime Service (that will preferentially call an
PSCI - ARM Power State Coordination Interface - Secure Monitor Call (SMC
- think SMI-like) internally to perform the shutdown/reboot) for the
action of powering off or resetting 64-bit ARM SBBR platforms.

Therefore if the alternative of an ACPI-based power off solution were
not initially supported, I don't think it would have much practical
impact, and it could be addressed after the initial support merged.

That's just my $0.02.

Jon.

[0] The Server Base Boot Requirements are the platform specification we
created for 64-bit ARM servers. They mandate the use of EFI and ACPI in
compliant platforms:
http://infocenter.arm.com/help/topic/com.arm.doc.den0044a/Server_Base_Boot_Requirements.pdf

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