linux-kernel - Re: [PATCH/RFC 0/2] regulator: bd9571mwv: Add support for toggle power switches

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Date:   Wed, 18 Apr 2018 15:29:36 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Marek Vasut <marek.vasut+renesas@...il.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>
Cc:     Linux PM list <linux-pm@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH/RFC 0/2] regulator: bd9571mwv: Add support for toggle
 power switches

Hi all,

On Wed, Mar 14, 2018 at 12:26 PM, Geert Uytterhoeven
<geert+renesas@...der.be> wrote:
> 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[1] 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 proposes a new callback for wake-up change
> notification, which allows performing step 1 when the user writes
> "enabled" to the PMIC's "wakeup" virtual file in sysfs, e.g.
>
>     echo enabled > /sys/devices/platform/soc/e60b0000.i2c/i2c-7/7-0030/bd9571mwv-regulator.2.auto/power/wakeup
>
> Conversely, writing "disabled" reverts the role of the accessory switch
> to a power switch.
> Note that unlike with momentary switches, backup mode is not enabled by
> default, as enabling it prevents the board from being powered off using
> the power switch, which may confuse the user.
>
> This has been tested on M3ULCB (thanks Jacopo!), and on Salvator-X(S).
>
> For testing, driver and DTS patches are available in the
> topic/bd9571-ddr-backup-mode-driver-v2 and
> topic/bd9571-ddr-backup-mode-dt-v2 branches of my renesas-drivers git
> repository at
> git://git.kernel.org/pub/scm/linux/kernel/git/geert/renesas-drivers.git.
>
> Thanks for your comments!
>
> [1] https://lkml.org/lkml/2018/3/14/302
>
> Geert Uytterhoeven (2):
>   PM / wakeup: Add callback for wake-up change notification
>   regulator: bd9571mwv: Add support for toggle power switches
>
>  drivers/base/power/wakeup.c             |  4 ++++
>  drivers/regulator/bd9571mwv-regulator.c | 24 ++++++++++++++++++++++++
>  include/linux/pm.h                      |  1 +
>  3 files changed, 29 insertions(+)

Any comments/suggestions?

In case you lost the patches from the thread:
https://www.spinics.net/lists/linux-renesas-soc/msg24955.html

Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds