From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lothar =?UTF-8?B?V2HDn21hbm4=?= Subject: Re: [RFC PATCH 1/2] dt-bindings: pwm: imx: Allow switching PWM output between PWM and GPIO Date: Thu, 23 Aug 2018 13:19:35 +0200 Message-ID: <20180823131935.1eae184f@ipc1.ka-ro> References: <1534862333-27950-1-git-send-email-michal.vokac@ysoft.com> <1534862333-27950-2-git-send-email-michal.vokac@ysoft.com> <20180823123759.68b78e9f@jawa> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Return-path: In-Reply-To: <20180823123759.68b78e9f@jawa> Sender: linux-kernel-owner@vger.kernel.org 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 List-Id: devicetree@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 ___________________________________________________________