RE: [PATCH/RFC v4 2/4] regulator: fixed: add regulator_ops members for suspend/resume

From: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
To: Mark Brown <broonie@kernel.org>
Cc: "ulf.hansson@linaro.org" <ulf.hansson@linaro.org>,
	Sudeep Holla <sudeep.holla@arm.com>,
	"lgirdwood@gmail.com" <lgirdwood@gmail.com>,
	"geert+renesas@glider.be" <geert+renesas@glider.be>,
	"magnus.damm@gmail.com" <magnus.damm@gmail.com>,
	"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-renesas-soc@vger.kernel.org" 
	<linux-renesas-soc@vger.kernel.org>
Subject: RE: [PATCH/RFC v4 2/4] regulator: fixed: add regulator_ops members for suspend/resume
Date: Tue, 30 Jun 2020 08:29:09 +0000	[thread overview]
Message-ID: <TY2PR01MB3692F64AB29BD83203CFC802D86F0@TY2PR01MB3692.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <20200629125756.GC5499@sirena.org.uk>

Hi Mark,

> From: Mark Brown, Sent: Monday, June 29, 2020 9:58 PM
> 
> On Mon, Jun 29, 2020 at 02:42:26AM +0000, Yoshihiro Shimoda wrote:
> > > From: Mark Brown, Sent: Friday, June 26, 2020 11:39 PM
> 
> Copying in Sudeep for the feedback on firmware interfaces.

Thank you very much for the discussion about the firmware.

> > > According to the changelog this is all about reflecting changes in the
> > > system state done by firmware but there's no interaction with firmware
> > > here which means this will be at best fragile.  If we need to reflect
> > > changes in firmware configuration I'd expect there to be some
> > > interaction with firmware about how it is configured, or at least that
> > > the configuration would come from the same source.
> 
> > I should have described background of previous patch series though,
> > according to previous discussion [1] the firmware side (like PSCI) is
> > also fragile unfortunately... So, I thought using regulator-off-in-suspend
> > in a regulator was better.
> 
> > On other hand, Ulf is talking about either adding a property (perhaps like
> > regulator-off-in-suspend) into a regulator or just adding a new property
> > into MMC [2]. What do you think about Ulf' comment? I'm thinking
> > adding a new property "full-pwr-cycle-in-suspend" is the best solution.
> > This is because using a regulator property and reflecting a state of regulator without
> > firmware is fragile, as you said.
> 
> TBH I worry about a property drifting out of sync with the firmware on
> systems where the firmware can be updated.

I understood it.

>  Personally my default
> assumption would always be that we're going to loose power for anything
> except the RAM and whatever is needed for wake sources during suspend so
> I find the discussion a bit surprising but in any case that seems like a
> better option than trying to shoehorn things in the way the series here
> did.

Thank you for your comment! So, I'll make such a patch series later.

>  Like I said in my earlier replies if this is done through the
> regulator API I'd expect it to be via the suspend interface.

I don't intend to use any regulator API for this issue for now.

Best regards,
Yoshihiro Shimoda

> > [1]
> > https://lore.kernel.org/linux-renesas-soc/CAMuHMdXjU7N4oG89YsozGijMpjgKGN6ezw2qm6FeGX=JyRhsvg@mail.gmail.com/
> >
> > [2]
> > https://lore.kernel.org/linux-renesas-soc/CAPDyKFpiBU1D+a7zb+Ggm0_HZ+YR4=LXJZ5MPytXtT=uBEdjPA@mail.gmail.com/
> >
> > Best regards,
> > Yoshihiro Shimoda
> >