On Wed, Oct 08, 2014 at 11:00:11AM +0200, Linus Walleij wrote: > On Tue, Oct 7, 2014 at 10:28 PM, Doug Anderson <diand...@chromium.org> wrote: > > > For pinctrl the "default" state is applied to pins before the driver's > > probe function is called. This is normally a sensible thing to do, > > but in some cases can cause problems. That's because the pins will > > change state before the driver is given a chance to program how those > > pins should behave. > > > > As an example you might have a regulator that is controlled by a PWM > > (output high = high voltage, output low = low voltage). The firmware > > might leave this pin as driven high. If we allow the driver core to > > reconfigure this pin as a PWM pin before the PWM's probe function runs > > then you might end up running at too low of a voltage while we probe. > > > > Let's introudce a new "init" state. If this is defined we'll set > > pinctrl to this state before probe and then "default" after probe > > (unless the driver explicitly changed states already). > > > > An alternative idea that was thought of was to use the pre-existing > > "sleep" or "idle" states and add a boolean property that we should > > start in that mode. This was not done because the "init" state is > > needed for correctness and those other states are only present (and > > only transitioned in to and out of) when (optional) power management > > is enabled. > > > > Signed-off-by: Doug Anderson <diand...@chromium.org> > > I *like* this approach. A lot. > > It will come with DT bindings for free as it's just strings. > > > +++ b/drivers/base/dd.c > > @@ -308,6 +308,8 @@ static int really_probe(struct device *dev, struct > > device_driver *drv) > > goto probe_failed; > > } > > > > + pinctrl_init_done(dev); > > We will need Greg's ACK for this oneliner.
As much as I hate subsystem-specific code in the driver core, I guess I let this happen before, so I can't object here :) Acked-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
