Hi, On Wed, Jun 14, 2023 at 12:03 PM Amit Pundir <amit.pundir@xxxxxxxxxx> wrote: > > On Wed, 7 Jun 2023 at 04:59, Doug Anderson <dianders@xxxxxxxxxxxx> wrote: > > > > From a black box perspective, I guess the things I could think of > > would be to keep poking around with things that you control. Best > > ideas I have: > > > > 1. Use "bisect" style techniques to figure out how much you really > > need to move the "lvs" regulators. Try moving it halfway up the list. > > If that works, move it closer to the bottom. If that doesn't work, > > move it closer to the top. Eventually you'd find out which regulator > > it's important to be before. > > Hi, I tried this bisect style technique to move lvs regulators up in > the list gradually and I found that they need to be enabled atleast > before ldo12 and the ldo regulators which follow the ldo12 in the > list. Super weird. I was hoping that something would jump out, but nothing does. :( I don't understand how lvs1 / lvs2 could have any impact on ldo12. :( > > 2. Try adding some delays to some of the regulators with > > "regulator-enable-ramp-delay" and/or "regulator-settling-time-us". > > Without a scope, it'll be tricky to figure out exactly which > > regulators might need delays, but you could at least confirm if the > > "overkill" approach of having all the regulators have some delay > > helps... I guess you could also try putting a big delay for "ldo26". > > If that works, you could try moving it up (again using a bisect style > > approach) to see where the delay matters? > > I tried this approach as well earlier today but I don't know how big > "the big" delay can be. The device fails to boot if I add a settling > time of as much as 2sec per each ldo and lvs regulator too. I didn't > try increasing the delay further. Yeah, 2 seconds is plenty big. If that doesn't fix it then it's not a timing issue. I guess with the above results, I'm still super confused about why the async probe has any impact at all on this. It sounds like the _ordering_ of the rpmh-regulators init matters but not the timing, and I'd expect the ordering to be the same between normal probe and async probe. Specifically, I think: a) There is exactly one rpmh-regulator driver instance in your system, right? b) Regulator initialization happens in rpmh_regulator_probe(). c) The rpmh_regulator_probe() function is itself synchronous. That is, it sets up one regulator at a time and, I believe, nothing about the behavior of rpmh_regulator_probe() changes for async vs. sync probe. ...so I'm left baffled...
