From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755122AbbCXRc0 (ORCPT ); Tue, 24 Mar 2015 13:32:26 -0400 Received: from opensource.wolfsonmicro.com ([80.75.67.52]:48851 "EHLO opensource.wolfsonmicro.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753366AbbCXRFg (ORCPT ); Tue, 24 Mar 2015 13:05:36 -0400 Date: Tue, 24 Mar 2015 17:05:34 +0000 From: Charles Keepax To: Mark Brown Cc: patches@opensource.wolfsonmicro.com, lgirdwood@gmail.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] regulator: arizona-ldo1: Add ramp time for HI_PWR Message-ID: <20150324170534.GK23705@opensource.wolfsonmicro.com> References: <1427207276-28038-1-git-send-email-ckeepax@opensource.wolfsonmicro.com> <20150324160609.GD17265@sirena.org.uk> <20150324164050.GI23705@opensource.wolfsonmicro.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150324164050.GI23705@opensource.wolfsonmicro.com> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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