* Linus Walleij <[email protected]> [130611 13:05]: > From: Linus Walleij <[email protected]> > > This document snippet tries to be helpful and define the pin > PM states and helpers, and how they should be used to create > some kind of common ontology around this. > > Cc: Ulf Hansson <[email protected]> > Cc: Kevin Hilman <[email protected]> > Cc: Tony Lindgren <[email protected]> > Signed-off-by: Linus Walleij <[email protected]> > --- > Documentation/pinctrl.txt | 118 > ++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 118 insertions(+) > > diff --git a/Documentation/pinctrl.txt b/Documentation/pinctrl.txt > index f6e664b..a34ea92 100644 > --- a/Documentation/pinctrl.txt > +++ b/Documentation/pinctrl.txt > @@ -1196,6 +1196,124 @@ registered. Thus make sure that the error path in > your driver gracefully > cleans up and is ready to retry the probing later in the startup process. > > > +Default and power management related states > +=========================================== > + > +As mentioned earlier the device core will automatically try to obtain a > +pinctrl handle and activate the "default" state on all drivers. > + > +However, for power management and power saving, it is sometimes necessary > +to switch pin states at runtime. Electrically speaking this involves > +for example reconfigure some pins to be grounded or pulled-down when the > +system as a whole goes to sleep, or a pull-up could be turned off when pins > +are idle, reducing leak current. > + > +To help out with this, if CONFIG_PM is selected in the Kconfig, three > +additional states will also be obtained by the driver core and cached > +there: > + > +"active" this is indended as an explicit active state, if the "default" > + state is not synonymous with the active one. > + > +"idle" this is a state that is relaxing the pins when the system as a > + whole is up and running, but these particular pins are unused. > + > +"sleep" this is a state that is used when the whole system goes to > + suspend, becomes uninteractive, unresponsive to anything but > + specific wake-up events.
In the cases I've seen "idle" and "sleep" are the same. But it sounds like other people's hardware have different needs and it's optional so: Acked-by: Tony Lindgren <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
