Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753485AbbGIRUx (ORCPT ); Thu, 9 Jul 2015 13:20:53 -0400 Received: from mail-wi0-f169.google.com ([209.85.212.169]:36708 "EHLO mail-wi0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753243AbbGIRUo (ORCPT ); Thu, 9 Jul 2015 13:20:44 -0400 Date: Thu, 9 Jul 2015 18:20:38 +0100 From: Lee Jones To: Doug Anderson Cc: Boris Brezillon , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "broonie@kernel.org" , kernel@stlinux.com, Liam Girdwood , Heiko =?iso-8859-1?Q?St=FCbner?= Subject: Re: [PATCH v2 0/9] regulator: pwm-regulator: Introduce continuous-mode Message-ID: <20150709172038.GA12199@x1> References: <1436281613-899-1-git-send-email-lee.jones@linaro.org> <20150709083041.3b203eb1@bbrezillon> <20150709115158.GA3445@x1> <20150709151429.6daf8fcb@bbrezillon> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2668 Lines: 58 On Thu, 09 Jul 2015, Doug Anderson wrote: > On Thu, Jul 9, 2015 at 6:14 AM, Boris Brezillon > wrote: > >> If you wish to add a 3rd mode, then I'm sure Mark will accept > >> submissions, but I think what you are suggesting would be pretty > >> complex and out-of-scope of what this patch-set is trying to achieve. > > > > Okay, still don't get the need to add a new mode which is almost doing > > the same thing when we could have implemented it in a generic way in the > > first place. But if your version has already been accepted then I think > > I'll have to propose a new mode :-/. > > > >> > >> As a side note, then if the voltage isn't directly proportional to the > >> duty cycle on a large scale i.e. max => min, then it will not likely > >> be very accurate between say table entries 1 => 2, or 4 => 5, etc. > >> > >> What I suggest you do in your case is provide a larger table with all > >> of the values you find interesting, as it sounds like your PWM > >> regulator isn't doing what one would normally expect. > > > > Well, I do not exactly agree here. Yes if you want to have a precise > > mapping you'll have to add more entries in your voltage table, but > > using linear interpolation between two points can be precise enough on > > some ranges and prevent one to define a complete voltage table in the > > DT. > > > > Doug, could give more details about the regulator used on the veyron > > board ? > > There's no need for a new mode as far as veyron is concerned. The pwm > regulator on veyron (as far as I understand it) acts the way that Lee > describes. Try doing the math on the values in the table and you > should see that it's as linear as it can be while still using integral > duty cycles. > > Originally I only suggested using "linear interpolation" because: > > * It meant no bindings change, which is always nice to avoid. > > * It meant that old devices got this new mode, which is probably the > right thing anyway (I think). Maybe nobody has published DTS files > with pwm-regulator, so the point is moot. Great news. This means that you provide the voltage the regulator will provide with 0% duty cycle and 100% duty cycle and you're hot to trot. No further configuration/bindings required. -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/