[PATCH/RFC 4/5] regulator: bd9571mwv: Add support for backup mode

Hi Mark,

On Wed, Oct 18, 2017 at 1:02 PM, Mark Brown [off-list ref] wrote:

On Tue, Oct 10, 2017 at 05:26:17PM +0200, Geert Uytterhoeven wrote:

quoted

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 :-(

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-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