On Thu, Sep 21, 2017 at 6:14 PM, Tomasz Figa [off-list ref] wrote:

This isn't a very good example, because pin-con-pdn and pin-pud-pdn
are used to program dedicated sleep state registers in the pin
controller and they can be programmed at any time. Typically one would
include them in "default" state.

Yeah. Baolin added a special flag "sleep-hardware-state" to
indicate these special states, so the pin control driver can set them
up at first state instantiation.

As for pins which don't have dedicated sleep state registers, i.e. the
alive banks, which retain their value, the DT node of device
associated with the pins would have "sleep" pinctrl state and its
driver would activate it on suspend.

Correct.

The only remaining use case would be pins in alive banks not
associated with any device, but I can't imagine any practical case
that would need to change the value on suspend in such case.

I think those could be made to work with hogs.

What also came up recently was pin controllers that
per se loose their state when the system suspends, so
the whole pin controller is kind of power-cycled and comes
up in some default state.

Florian is looking into a generic solution to that problem.

Yours,
Linus Walleij