linux-kernel - Re: [PATCH v3 0/3] regulator: bd9571mwv: Add support for toggle power switches

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Message-ID: <20180715165749.GA10023@amd>
Date:   Sun, 15 Jul 2018 18:57:49 +0200
From:   Pavel Machek <pavel@....cz>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Marek Vasut <marek.vasut+renesas@...il.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, linux-pm@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/3] regulator: bd9571mwv: Add support for toggle
 power switches

Hi!

> The ROHM BD9571MWV PMIC on the Renesas Salvator-X(S) and ULCB
> development boards supports DDR Backup Power, which means that the DDR
> power rails can be kept powered while the main SoC is powered down.
> 
> This patch series extends the support for DDR backup mode (see commit
> 6eb0bfae6973eb6a ("regulator: bd9571mwv: Add support for backup mode"))
> to systems with toggle instead of momentary power switches.
> 
> With a toggle power switch (or level signal), the following steps must
> be followed exactly:
>    1. Configure PMIC for backup mode, which changes the role of the
>       power switch to a wake-up switch, 
>    2. Switch accessory power switch off, to prepare for system suspend,
>       which is a manual step not controlled by software,
>    3. Suspend system,
>    4. Switch accessory power switch on, to resume.
> 
> Unlike on systems with a momentary toggle switch, an additional step 2
> must be performed in between step 1 and step 3.  Hence step 1 can no
> longer be handled in the PMIC's suspend callback.
> 
> This patch series allows performing step 1 when the user writes
> "on" to the PMIC's "backup_mode" virtual file in sysfs, e.g.
> 
>     echo on > /sys/bus/i2c/drivers/bd9571mwv/*/bd9571mwv-regulator*/backup_mode

Do you expect more boards to have similar design?

If so, we may want to have standard place in /sys/ not depending on
i2c paths and driver names, but I believe such design is so... awkward
that it is not going to appear anywhere else...?

								Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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