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Date: Tue, 24 Mar 2015 17:05:34 +0000 From: Charles Keepax <ckeepax@...nsource.wolfsonmicro.com> To: Mark Brown <broonie@...nel.org> Cc: patches@...nsource.wolfsonmicro.com, lgirdwood@...il.com, linux-kernel@...r.kernel.org Subject: Re: [PATCH] regulator: arizona-ldo1: Add ramp time for HI_PWR On Tue, Mar 24, 2015 at 04:40:50PM +0000, Charles Keepax wrote: > On Tue, Mar 24, 2015 at 09:06:09AM -0700, Mark Brown wrote: > > On Tue, Mar 24, 2015 at 02:27:56PM +0000, Charles Keepax wrote: > > > > > +static int arizona_ldo1_hc_set_voltage_time_sel(struct regulator_dev *rdev, > > > + unsigned int old_selector, > > > + unsigned int new_selector) > > > +{ > > > + /* if moving to 1.8v allow time for it to reach voltage */ > > > + if (new_selector == rdev->desc->n_voltages - 1) > > > + return 25; > > > + else > > > + return 0; > > > +} > > > > So changes to move to the top voltage always take constant time while > > all other voltage changes are instantaneous? That doesn't seem right. > > I'd expect something more like a calculation based on some number of > > miliseconds per milivolt. > > Its more just that this is the only case that we really care > about. The reg only ever gets used at 1.2V and 1.8V, and the > only case where there is a problem is if we ask for 1.8V and > we don't have it yet. > > I don't think we really have the data to give for other cases. I > could expand the comment perhaps? Or TBH it is fast enough it is > unlikely to ever be a problem in practice so we could just drop > the patch. Oh, I had one other thought, what about if we just returned 25uS as a worse case for the transition. Perhaps that would be nicer, and the 1.2V -> 1.8V transition is almost certainly the slowest of the options available. Thanks, Charles -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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