On 12/11/2022 17.54, Jonathan Cameron wrote: > On Fri, 11 Nov 2022 15:39:18 +0100 > Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx> wrote: > >> The ad74412r/ad74413r has an internal 2.5V reference output, which (by >> tying the REFOUT pin to the REFIN pin) can be used in lieu of an >> external 2.5V input reference. So stop marking refin-supply as >> required. >> >> Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx> > > > Interesting corner case. Given we have no way of knowing if the > wiring has REFOUT connected to REFIN I see two ways we should fix this. > > 1) Just have any DT doing this provide a fixed regulator. > 2) Have the REFOUT supported as an actual regulator - in theory it might be > wired to other devices. This might get a little interesting ordering > wise as we'll want to register the regulator before we try to consume > it in the same driver. I'm also not 100% sure there are no other issues > in a driver providing and consuming the same regulator. Hm, I don't like the idea of exposing REFOUT as a real regulator. As you write, there's gonna be interesting chicken-and-egg problems, and I also don't think it can actually deliver any meaningful current, i.e. it can't really (and shouldn't) be used for supplying other peripherals. A third option is to have a boolean property to explicitly indicate that "yes, we're using refout as refin", and then make the requirement in the schema be "refin-supply XOR refout-as-refin". But I think the simplest is (1), I will just add a fixed-regulator with a suitable comment in my .dts, and patches 2,3 can be ignored. Thanks, Rasmus
