El Fri, Oct 28, 2016 at 07:15:21PM +0100 Mark Brown ha dit: > On Mon, Sep 26, 2016 at 10:41:59AM -0700, Doug Anderson wrote: > > > I guess I think of the whole network of components as the PWM > > regulator and not the individual discreet BUCK. I'm also not quite > > sure how you would model it as you're asking. I suppose you could say > > that all of the resistors / capacitors / inductors end up producing a > > voltage and this voltage is an input to the BUCK. ...then the BUCK > > Yes, that's what's happening. > > > I know for sure that our EEs have massively modified the behavior of > > the whole thing by just changing the resistors / capacitors / > > inductors, changing the undershoot, OVP issue, voltage ranges, default > > voltage, etc. That's what leads me to believe it's not so separable. > > What you're describing to me is a discrete DCDC that has an input > voltage that sets the output voltage which happens to be set with a PWM. > It's of course going to be the case that the passives are important to > the system performance but it seems we have two bits here - the PWM > regulator providing an input to the DCDC and the DCDC itself which is > sensitive to rate changes. I experimented a bit with this. Besides the question of how to model the passives I wonder how the two regulators would interact. The correct thing seems to be to specify the input regulator as a supply of the DCDC. dcdc->set_voltage breaks down a voltage transition into steps (if needed) and calls regulator_set_voltage(supply) for each step. The problem with that is that regulator_set_voltage(dcdc) acquires the supply lock(s), later regulator_set_voltage(supply) tries to acquire its own lock which is already held. This can be worked around by only using the supply regulator in the DCDC, but not specify it as a supply. However this seems more a hack than a proper solution. Am I missing something obvious here or approaching this from a wrong angle? Thanks Matthias -- 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
