Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755862Ab2KHNt3 (ORCPT ); Thu, 8 Nov 2012 08:49:29 -0500 Received: from mail-vb0-f46.google.com ([209.85.212.46]:35316 "EHLO mail-vb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752356Ab2KHNt2 (ORCPT ); Thu, 8 Nov 2012 08:49:28 -0500 MIME-Version: 1.0 In-Reply-To: <509BAFB9.6090801@antcom.de> References: <20121106181939.61c50233@avionic-0020.adnet.avionic-design.de> <1352301955-15960-1-git-send-email-alban.bedel@avionic-design.de> <509B80A7.1060700@antcom.de> <20121108113353.4fdbb25c@avionic-0020.adnet.avionic-design.de> <509B8D20.6070208@antcom.de> <20121108122345.72aa0f6c@avionic-0020.adnet.avionic-design.de> <509BAFB9.6090801@antcom.de> Date: Thu, 8 Nov 2012 11:49:27 -0200 Message-ID: Subject: Re: [PATCH] pwm: lpc32xx - Fix the PWM polarity From: Alexandre Pereira da Silva To: Roland Stigge Cc: Alban Bedel , Thierry Reding , LKML Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1392 Lines: 42 On Thu, Nov 8, 2012 at 11:12 AM, Roland Stigge wrote: > On 08/11/12 12:23, Alban Bedel wrote: >>>> It is intended, the formular for duty value in the register is: >>>> >>>> duty = (256 - 256*duty_ns/period_ns) % 256 >>> >>> Where does this modulo defined? In the Manual, there is sth. like this >>> defined for RELOADV (tables 606+607), but not for DUTY. >>> >>> Maybe I missed sth. in the manual. Link or hint appreciated! >> >> The manual doesn't mention this explicitly but you can see that without >> the modulo when duty_ns==0 DUTY would be 256, but the register is only >> 8 bits wide (ie. modulo 256). I made a few test and looked at the PWM >> output on a scope they confirm this: >> >> DUTY HIGH LEVEL >> 1 99.9% >> 25 90.0% >> 128 50.0% >> 220 10.0% >> 255 0.1% >> 0 0.0% >> >> I'll resubmit the patch with the clamping in the correct order. > > Thanks for measuring. With this, your resubmitted patch make much more > sense now. > > Roland Alban, I think you should include this measurements on the source code as comments, for future reference. Thanks. -- 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/