linux-kernel - Re: System suspend states and device driver suspend() callback

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Date:	Mon, 26 Aug 2013 16:50:53 +0800
From:	Li Yang <leoli@...escale.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Li Yang-R58472 <r58472@...escale.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: System suspend states and device driver suspend() callback

On Sat, Aug 17, 2013 at 7:53 AM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> On Friday, August 16, 2013 05:13:42 PM Li Yang-R58472 wrote:
>>
>> 在 2013-8-16，下午7:22，"Rafael J. Wysocki" <rjw@...k.pl> 写道：
>>
>> > On Friday, August 16, 2013 04:06:26 PM Li Yang wrote:
>> >> Hi Guys,
>> >>
>> >> Is there a standard way for the device drivers to know if the system
>> >> is going to “standby” mode or “mem” mode when the suspend() callbacks
>> >> are called?
>> >
>> > No, there's none.
>> >
>> > What do you need that for?
>>
>> Some chips like ours are putting the on-chip devices into different low
>> power states when entering different system low power states.  When we enter
>> system standby, on-chip devices are clock gated.  While entering suspend to
>> ram, on-chip devices are power gated.  We want to driver to act differently
>> too when entering different suspend states.
>
> Can you possibly use platform suspend operations to implement that (in analogy
> with ACPI suspend operations)?

I agree it's best to get the state that the device will be in during
suspend from the platform code.  Will it be better to have a standard
interface to pass this information?  Given the fact that a single
device can be used by different platforms even different architecture
nowadays.  How about exposing some new callbacks from the
platform_suspend_ops for the driver to use?

Regards,
Leo
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