From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8368DC4BA12 for ; Wed, 26 Feb 2020 15:10:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5F4F82468C for ; Wed, 26 Feb 2020 15:10:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728002AbgBZPKh (ORCPT ); Wed, 26 Feb 2020 10:10:37 -0500 Received: from metis.ext.pengutronix.de ([85.220.165.71]:38089 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727670AbgBZPKg (ORCPT ); Wed, 26 Feb 2020 10:10:36 -0500 Received: from pty.hi.pengutronix.de ([2001:67c:670:100:1d::c5]) by metis.ext.pengutronix.de with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1j6yKY-0004aS-Th; Wed, 26 Feb 2020 16:10:34 +0100 Received: from ukl by pty.hi.pengutronix.de with local (Exim 4.89) (envelope-from ) id 1j6yKY-0007AG-J5; Wed, 26 Feb 2020 16:10:34 +0100 Date: Wed, 26 Feb 2020 16:10:34 +0100 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Matthias Schiffer Cc: thierry.reding@gmail.com, linux-pwm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/4] pwm: pca9685: remove unused duty_cycle struct element Message-ID: <20200226151034.7i3h5blmrwre2yzg@pengutronix.de> References: <20200226135229.24929-1-matthias.schiffer@ew.tq-group.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200226135229.24929-1-matthias.schiffer@ew.tq-group.com> User-Agent: NeoMutt/20170113 (1.7.2) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c5 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Matthias, as you seem to have this hardware on your desk, it would be great if you could answer the following questions: - Does the hardware complete the currently running period before applying a new setting? - Is this racy somehow (i.e. can it happen that when going from duty_cycle/period = 1000/5000 to duty_cycle/period = 4000/10000 the output is 1000/10000 (or 4000/5000) for one cycle)? - Does the hardware complete the currently running period before .enabled = false is configured? - How does the output pin behave on a disabled PWM. (Usual candidates are: freeze where is just happens to be, constant inactive and High-Z). Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | https://www.pengutronix.de/ |