Hi, On Wed, May 30, 2018 at 9:36 AM, Mark Brown <broonie@xxxxxxxxxx> wrote: > On Wed, May 30, 2018 at 09:31:55AM -0700, Doug Anderson wrote: >> On Wed, May 30, 2018 at 9:13 AM, Mark Brown <broonie@xxxxxxxxxx> wrote: > >> > If we're just going to use the most recently set voltage then hopefully >> > the hardware already knew that, and it might not be the lowest available >> > voltage if the last consumer to get turned off was holding the voltage >> > higher. > >> To circle back to the original point: the problem is that (IMHO) the >> hardware is doing the wrong thing by still counting Linux's vote for a >> voltage even though Linux also voted that the regulator should be >> disabled. So basically we're working around the hardware by >> pretending to vote for a dummy lower voltage whenever Linux wants the >> regulator disabled. From Linux's point of view everything works as >> normal--we just tell the hardware a falsehood so it doesn't count our >> vote for a voltage while the regulator is disabled. > > Yeah, and I don't think that's unreasonable for the core to do - just > drop the voltage to the constraint minimum after it has turned off the > regulator, then recheck and raise if needed before it enables again. Would it do this for all regulators, though? Most regulators are hooked up over a slow i2c bus, so that means that every regulator disable would now do an extra i2c transfer even though for all regulators (other than RPMh) the voltage of a regulator doesn't matter when it's been "disabled' (from Linux's point of view). Hrmmm, I suppose maybe it'd be OK though because for most regulators we'd use "regcache" and most regulators that we enabled/disable a lot are not expected to change voltage in Linux (so the regcache write would hopefully be a noop), so maybe it wouldn't be _that_ inefficient... -Doug -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
