From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexandre Belloni Subject: Re: [PATCHv6 0/3] pwm: imx: support output polarity inversion Date: Mon, 12 Sep 2016 14:45:53 +0200 Message-ID: <20160912124553.aqgv7b4vsx4urogi@piout.net> References: <20141009151605.GA8818@ulmo.nvidia.com> <1412950949-7505-1-git-send-email-LW@KARO-electronics.de> <6c896634c4d6446df0388da2c0228232@agner.ch> <20160909091857.7a263220@ipc1.ka-ro> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Return-path: Received: from down.free-electrons.com ([37.187.137.238]:55599 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1758050AbcILMp4 (ORCPT ); Mon, 12 Sep 2016 08:45:56 -0400 Content-Disposition: inline In-Reply-To: <20160909091857.7a263220@ipc1.ka-ro> Sender: linux-pwm-owner@vger.kernel.org List-Id: linux-pwm@vger.kernel.org To: Lothar =?iso-8859-1?Q?Wa=DFmann?= Cc: Stefan Agner , linux-pwm@vger.kernel.org, Sascha Hauer , Thierry Reding , linux-arm-kernel@lists.infradead.org, Shawn Guo On 09/09/2016 at 09:18:57 +0200, Lothar Waßmann wrote : > Hi, > > On Thu, 08 Sep 2016 15:15:57 -0700 Stefan Agner wrote: > > On 2014-10-10 07:22, Lothar Waßmann wrote: > > > This patch series adds support for polarity inversion to the pwm-imx > > > driver. The patches have been tested on i.MX6, i.MX53 and with the > > > ti-ehrpwm.c driver. > > > > Do you know what prevented this patchset from getting merged? > > > No idea. > > > We are looking for Polarity support in PWM for too, this is especially > > useful for backlight control. > > > Actually the PWM driver may be the wrong place to achieve this. When > the backlight driver sets the brightness to 0 to switch the backlight > off, it will disable the PWM. This will make the PWM pin go LOW and > thus turn the backlight to full brightness rather than off (unless there > is an additional GPIO that controls a backlight enable pin on the LCD). > Isn't a properly designed PWM putting a high level on its pin when disabled and configured with inversed polarity ? If the HW is capable of it, the driver should be fixed. -- Alexandre Belloni, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com From mboxrd@z Thu Jan 1 00:00:00 1970 From: alexandre.belloni@free-electrons.com (Alexandre Belloni) Date: Mon, 12 Sep 2016 14:45:53 +0200 Subject: [PATCHv6 0/3] pwm: imx: support output polarity inversion In-Reply-To: <20160909091857.7a263220@ipc1.ka-ro> References: <20141009151605.GA8818@ulmo.nvidia.com> <1412950949-7505-1-git-send-email-LW@KARO-electronics.de> <6c896634c4d6446df0388da2c0228232@agner.ch> <20160909091857.7a263220@ipc1.ka-ro> Message-ID: <20160912124553.aqgv7b4vsx4urogi@piout.net> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 09/09/2016 at 09:18:57 +0200, Lothar Wa?mann wrote : > Hi, > > On Thu, 08 Sep 2016 15:15:57 -0700 Stefan Agner wrote: > > On 2014-10-10 07:22, Lothar Wa?mann wrote: > > > This patch series adds support for polarity inversion to the pwm-imx > > > driver. The patches have been tested on i.MX6, i.MX53 and with the > > > ti-ehrpwm.c driver. > > > > Do you know what prevented this patchset from getting merged? > > > No idea. > > > We are looking for Polarity support in PWM for too, this is especially > > useful for backlight control. > > > Actually the PWM driver may be the wrong place to achieve this. When > the backlight driver sets the brightness to 0 to switch the backlight > off, it will disable the PWM. This will make the PWM pin go LOW and > thus turn the backlight to full brightness rather than off (unless there > is an additional GPIO that controls a backlight enable pin on the LCD). > Isn't a properly designed PWM putting a high level on its pin when disabled and configured with inversed polarity ? If the HW is capable of it, the driver should be fixed. -- Alexandre Belloni, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com