linux-kernel - Re: [PATCH/RFC 4/5] regulator: bd9571mwv: Add support for backup mode

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Message-ID: <20171018112419.3eqz34epcshxas3f@sirena.co.uk>
Date:   Wed, 18 Oct 2017 12:24:19 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Marek Vasut <marek.vasut+renesas@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Simon Horman <horms@...ge.net.au>,
        Magnus Damm <magnus.damm@...il.com>,
        Lee Jones <lee.jones@...aro.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH/RFC 4/5] regulator: bd9571mwv: Add support for backup mode

On Wed, Oct 18, 2017 at 01:19:08PM +0200, Geert Uytterhoeven wrote:
> On Wed, Oct 18, 2017 at 1:02 PM, Mark Brown <broonie@...nel.org> wrote:
> > On Tue, Oct 10, 2017 at 05:26:17PM +0200, Geert Uytterhoeven wrote:

> >> Backup mode is not enabled automatically, as e.g. on Renesas
> >> Salvator-X(S) boards enabling backup mode changes the role of the ACC
> >> switch from a power switch to a wake-up switch.  Hence enabling it
> >> prevents the board from being powered off using the ACC switch, which
> >> may confuse the user.

> > This sounds an awful lot like the standard power/wakeup, though the
> > power change is a bit unexpected there.  I'm also wondering if it makes
> > sense to just only enable the wakeup mode when suspending which
> > preserves the power off functionality while also keeping the wakeup
> > support.

> The ACC switch is not a momentary switch (push button), but a toggle
> switch with two positions.
> Hence you cannot enable wakeup mode while suspending, as the proper
> system suspend/resume procedure is:
>   1. Enable backup mode in the PMIC,
>   2. Switch ACC off (no-op as backup mode has been enabled),
>   3. Suspend to RAM (PSCI suspend) => system suspends,
>   4. Switch ACC on => system wakes up.
> If you would combine steps 1 and 3, you can no longer do step 2 in between.

> Yes, it's complicated :-(

I'm confused, I thought this was a physical switch but that's talking
about this as something software controlled (at least in step 2)?

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