Re: [RFC 1/2] PM / suspend: Add platform_suspend_target_state()

From: Alexandre Belloni <alexandre.belloni@free-electrons.com>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Florian Fainelli <f.fainelli@gmail.com>,
	Mason <slash.tmp@free.fr>, Pavel Machek <pavel@ucw.cz>,
	linux-kernel@vger.kernel.org,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	linux-pm <linux-pm@vger.kernel.org>,
	Thibaud Cornic <thibaud_cornic@sigmadesigns.com>,
	JB <jb_lescher@sigmadesigns.com>,
	Kevin Hilman <khilman@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [RFC 1/2] PM / suspend: Add platform_suspend_target_state()
Date: Sun, 16 Jul 2017 15:38:32 +0200	[thread overview]
Message-ID: <20170716133832.mnuaie4jnlwu6dwj@piout.net> (raw)
In-Reply-To: <3675920.H2f5xgTCgu@aspire.rjw.lan>

On 16/07/2017 at 12:22:08 +0200, Rafael J. Wysocki wrote:
> On Saturday, July 15, 2017 07:36:21 PM Florian Fainelli wrote:
> > 
> > On 07/15/2017 04:38 PM, Rafael J. Wysocki wrote:
> > > On Sunday, July 16, 2017 01:34:53 AM Mason wrote:
> > >> On 16/07/2017 01:24, Rafael J. Wysocki wrote:
> > >>
> > >>> On Saturday, July 15, 2017 10:20:27 AM Florian Fainelli wrote:
> > >>>
> > >>>> The enum offers the advantage of centralizing how many different states
> > >>>> exist for all the platforms we know about in the kernel, it's easy to
> > >>>> define common values for platforms that have the same semantics, just
> > >>>> like it's simple to add new values for platform specific details.
> > >>>
> > >>> Well, you seem to be liking this, so why don't you just implement it?
> > >>
> > >> At the end of his message, Florian wrote:
> > >>
> > >>> In any case, just agree and I will be happy to follow-up with patches.
> > > 
> > > But it may be hard to convince everybody without posting code changes
> > > and often enough showing a patch makes a good argument.
> > 
> > I had the patches ready last night, saw the emails this morning and
> > decided to go mountain bike for a bit to think about it some more. You
> > will find my follow-up patches that hopefully implement your recommendation.
> 
> OK, thanks!
> 
> There is one problem with this I missed before, though, sorry about that.
> 
> Drivers need to be able to distinguish between suspend-to-idle and the platform
> states too, so we need to store the argument passed to suspend_devices_and_enter()
> somewhere too, either in the core or in the platform code.
> 
> And if we need to store it anyway, let's just store it in the core in a global var
> (say pm_suspend_target_state), export that and be done.
> 
> There still will be a concern regarding drivers that care about differences between
> PM_SUSPEND_MEM and PM_SUSPEND_STANDBY, because those differences are
> platform-dependent, but let's defer addressing this until we have a driver
> that needs to run on different platforms with different definitions for those
> things.
> 

We already have the case for drivers/net/ethernet/cadence/ and
drivers/net/can/m_can/ and many of the at91 drivers. Depending on the
specific SoC they run on, PM_SUSPEND_MEM may or may not cut VDDcore or
may or may not change the peripheral clock.

-- 
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com