On Fri, Feb 10, 2023 at 10:18:14AM +0000, Andre Przywara wrote: > > > Not sure if you were actually arguing this, but the change I sketched > > > above (interpreting 0 as 24MHz/1) is separate though, as the current > > > default is "no DT property", and not 0. There is no input-debounce > > > property user in the kernel tree at the moment, so we wouldn't break > > > anyone. The only thing that would change is if a downstream user was > > > relying on "0" being interpreted as "skip the setup", which isn't > > > really documented and could be argued to be an implementation detail. > > > > > > So I'd suggest to implement 0 as "lowest possible", and documenting that > > > and the 32KHz/1 default if no property is given. > > > > Ah, my bad. > > > > There's another thing to consider: there's already a generic per-pin > > input-debounce property in pinctrl. > > > > Since we can't control it per pin but per bank, we moved it to the > > controller back then, but there's always been this (implicit) > > expectation that it was behaving the same way. > > > > And the generic, per-pin, input-debounce documentation says: > > > > > Takes the debounce time in usec as argument or 0 to disable debouncing > > > > I agree that silently ignoring it is not great, but interpreting 0 as > > the lowest possible is breaking that behaviour which, I believe, is a > > worse outcome. > > Is it really? If I understand the hardware manuals correctly, we cannot > really turn that feature off, so isn't the lowest possible time period (24 > MHz/1 at the moment) the closest we can get to "turn it off"? So > implementing this would bring us actually closer to the documented > behaviour? Or did I get the meaning of this time period wrong? > At least that's my understanding of how it fixed Andreas' problem: 1µs > is still not "off", but much better than the 31µs of the default. The new > 0 would then be 0.041µs. My point was that the property we share the name (and should share the semantics with) documents 0 as disabled. We would have a behavior that doesn't disable it. It's inconsistent. The reason doesn't really matter, we would share the same name but have a completely different behavior, this is super confusing to me. Maxime
