linux-kernel - Re: [PATCH] ACPI: PM: Export the function acpi_sleep_state

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Message-ID: <20190614223310.pwwoefu5qdvcuaiy@shell.armlinux.org.uk>
Date:   Fri, 14 Jun 2019 23:33:10 +0100
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Dexuan Cui <decui@...rosoft.com>
Cc:     Michael Kelley <mikelley@...rosoft.com>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>,
        "lenb@...nel.org" <lenb@...nel.org>,
        "robert.moore@...el.com" <robert.moore@...el.com>,
        "erik.schmauss@...el.com" <erik.schmauss@...el.com>,
        Russ Dill <Russ.Dill@...com>,
        Sebastian Capella <sebastian.capella@...aro.org>,
        Pavel Machek <pavel@....cz>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "apw@...onical.com" <apw@...onical.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        vkuznets <vkuznets@...hat.com>,
        "marcelo.cerri@...onical.com" <marcelo.cerri@...onical.com>
Subject: Re: [PATCH] ACPI: PM: Export the function
 acpi_sleep_state_supported()

Hi,

On Fri, Jun 14, 2019 at 10:19:02PM +0000, Dexuan Cui wrote:
> > -----Original Message-----
> > From: Michael Kelley <mikelley@...rosoft.com>
> > Sent: Friday, June 14, 2019 1:48 PM
> > To: Dexuan Cui <decui@...rosoft.com>; linux-acpi@...r.kernel.org;
> > rjw@...ysocki.net; lenb@...nel.org; robert.moore@...el.com;
> > erik.schmauss@...el.com
> > Cc: linux-hyperv@...r.kernel.org; linux-kernel@...r.kernel.org; KY Srinivasan
> > <kys@...rosoft.com>; Stephen Hemminger <sthemmin@...rosoft.com>;
> > Haiyang Zhang <haiyangz@...rosoft.com>; Sasha Levin
> > <Alexander.Levin@...rosoft.com>; olaf@...fle.de; apw@...onical.com;
> > jasowang@...hat.com; vkuznets <vkuznets@...hat.com>;
> > marcelo.cerri@...onical.com
> > Subject: RE: [PATCH] ACPI: PM: Export the function
> > acpi_sleep_state_supported()
> > 
> > It seems that sleep.c isn't built when on the ARM64 architecture.  Using
> > acpi_sleep_state_supported() directly in hv_balloon.c will be problematic
> > since hv_balloon.c needs to be architecture independent when the
> > Hyper-V ARM64 support is added.  If that doesn't change, a per-architecture
> > wrapper will be needed to give hv_balloon.c the correct information.  This
> > may affect whether acpi_sleep_state_supported() needs to be exported vs.
> > just removing the "static".   I'm not sure what the best approach is.
> > 
> > Michael
> 
> + some ARM experts who worked on arch/arm/kernel/hibernate.c.
> 
> drivers/acpi/sleep.c is only built if ACPI_SYSTEM_POWER_STATES_SUPPORT
> is defined, but it looks this option is not defined on ARM.
> 
> It looks ARM does not support the ACPI S4 state, then how do we know 
> if an ARM host supports hibernation or not?

Don't forget that Linux does not support ACPI on 32-bit ARM, which is
quite different from the situation on 64-bit ARM.

arch/arm/kernel/hibernate.c is only for 32-bit ARM, and is written with
the assumption that there is no interaction required with any firmware
to save state, and later restore state upon resuming.

Or am I missing something?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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