On 4.10.2023 16:17, Stephan Gerhold wrote: > Some regulator drivers do not provide a way to check if the regulator is > currently enabled or not. That does not necessarily mean that the > regulator is always-on. For example, the regulators managed by the RPM > firmware on Qualcomm platforms can be either on or off during boot but > the initial state is not known. To sync the state the regulator should > get either explicitly enabled or explicitly disabled. > > Enabling all regulators unconditionally is not safe, because we might > not know which voltages are safe. The devices supplied by those > regulators might also require a special power-up sequence where the > regulators are turned on in a certain order or with specific delay. > > Disabling all unused regulators is safer. If the regulator is already > off it will just stay that way. If the regulator is on, disabling it > explicitly allows the firmware to turn it off for reduced power > consumption. > > The regulator core already has functionality for disabling unused > regulators. However, at the moment it assumes that all regulators where > the .is_enabled() callback fails are actually off. There is no way to > return a special value for the "unknown" state to explicitly ask for > disabling those regulators. > > Some drivers (e.g. qcom-rpmh-regulator.c) return -EINVAL for the case > where the initial status is unknown. Use that return code to assume the > initial status is unknown and try to explicitly disable the regulator > in that case. > > Signed-off-by: Stephan Gerhold <stephan.gerhold@xxxxxxxxxxxxxxx> > --- > Instead of -EINVAL we could also use a different return code to indicate > the initial status is unknown. Or maybe there is some other option that > would be easier? This is working for me but I'm sending it as RFC to get > more feedback. :) -EOPNOTSUPP for "doesn't support getting is_enabled state"? I think this looks really good.. And will definitely help finding power hogs! At the cost of breaking booting with broken DTs. But as the name by which I referred to them suggests, this was never really destined to work.. Konrad
