From mboxrd@z Thu Jan  1 00:00:00 1970
From: jcm@redhat.com (Jon Masters)
Date: Tue, 17 Mar 2015 01:59:30 -0400
Subject: [update][PATCH v10 06/21] ACPI / sleep: Introduce
 CONFIG_ACPI_GENERIC_SLEEP
In-Reply-To: <5507A91A.1090206@huawei.com>
References: <1426234469-6434-1-git-send-email-hanjun.guo@linaro.org>
 <3737028.Ib0fKlgSkd@vostro.rjw.lan> <5507933F.2020203@huawei.com>
 <10995588.scpoK3KRg2@vostro.rjw.lan> <5507A91A.1090206@huawei.com>
Message-ID: <5507C2C2.1090509@redhat.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

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