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=-0.9 required=3.0 tests=FROM_EXCESS_BASE64, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 C8014C4321D for ; Thu, 23 Aug 2018 11:19:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 899D52152D for ; Thu, 23 Aug 2018 11:19:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 899D52152D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=KARO-electronics.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731417AbeHWOsx convert rfc822-to-8bit (ORCPT ); Thu, 23 Aug 2018 10:48:53 -0400 Received: from smtprelay07.ispgateway.de ([134.119.228.104]:20987 "EHLO smtprelay07.ispgateway.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729260AbeHWOsx (ORCPT ); Thu, 23 Aug 2018 10:48:53 -0400 Received: from [89.1.81.74] (helo=ipc1.ka-ro) by smtprelay07.ispgateway.de with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1fsneK-000539-I7; Thu, 23 Aug 2018 13:19:36 +0200 Date: Thu, 23 Aug 2018 13:19:35 +0200 From: Lothar =?UTF-8?B?V2HDn21hbm4=?= To: Lukasz Majewski Cc: Michal =?UTF-8?B?Vm9rw6HEjQ==?= , Thierry Reding , Rob Herring , Mark Rutland , devicetree@vger.kernel.org, linux-pwm@vger.kernel.org, linux-kernel@vger.kernel.org, Fabio Estevam Subject: Re: [RFC PATCH 1/2] dt-bindings: pwm: imx: Allow switching PWM output between PWM and GPIO Message-ID: <20180823131935.1eae184f@ipc1.ka-ro> In-Reply-To: <20180823123759.68b78e9f@jawa> References: <1534862333-27950-1-git-send-email-michal.vokac@ysoft.com> <1534862333-27950-2-git-send-email-michal.vokac@ysoft.com> <20180823123759.68b78e9f@jawa> Organization: Ka-Ro electronics GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT X-Df-Sender: bHdAa2Fyby1lbGVjdHJvbmljcy5kZQ== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Lukasz Majewski wrote: > Hi Michal, > > > Output of the PWM block of i.MX SoCs is always zero volts when the > > block is disabled. This can caue issues when inverted PWM polarity is > > needed. With inverted polarity a duty cycle = 0% corresponds to solid > > high level on the output. If the PWM is dissabled its output > > instantly goes to solid zero which corresponds to duty cycle = 100%. > > > > To have a trully inverted PWM output configure the PWM pad as a GPIO > > with pull-up. Then switch the pad to PWM output whenever non-zero > > duty cycle is needed. > > Just to ask - Is your display equipped with power supply enable/disable > pin? > > As fair as I remember the trick to avoid flickering the display > was to disable the display (enable-gpio property) and set the PWM PIN > as GPIO to high in u-boot. > Unfortunately there are both types of displays. Some with an ENABLE pin, some without. Lothar Waßmann -- ___________________________________________________________ Ka-Ro electronics GmbH | Pascalstraße 22 | D - 52076 Aachen Phone: +49 2408 1402-0 | Fax: +49 2408 1402-10 Geschäftsführer: Matthias Kaussen Handelsregistereintrag: Amtsgericht Aachen, HRB 4996 www.karo-electronics.de | info@karo-electronics.de ___________________________________________________________