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From: Alexandre Belloni <alexandre.belloni@free-electrons.com>
To: "Lothar Waßmann" <LW@KARO-electronics.de>
Cc: Stefan Agner <stefan@agner.ch>,
	linux-pwm@vger.kernel.org, Sascha Hauer <s.hauer@pengutronix.de>,
	Thierry Reding <thierry.reding@gmail.com>,
	linux-arm-kernel@lists.infradead.org,
	Shawn Guo <shawn.guo@linaro.org>
Subject: Re: [PATCHv6 0/3] pwm: imx: support output polarity inversion
Date: Mon, 12 Sep 2016 14:45:53 +0200	[thread overview]
Message-ID: <20160912124553.aqgv7b4vsx4urogi@piout.net> (raw)
In-Reply-To: <20160909091857.7a263220@ipc1.ka-ro>

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

WARNING: multiple messages have this Message-ID (diff)
From: alexandre.belloni@free-electrons.com (Alexandre Belloni)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCHv6 0/3] pwm: imx: support output polarity inversion
Date: Mon, 12 Sep 2016 14:45:53 +0200	[thread overview]
Message-ID: <20160912124553.aqgv7b4vsx4urogi@piout.net> (raw)
In-Reply-To: <20160909091857.7a263220@ipc1.ka-ro>

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

  reply	other threads:[~2016-09-12 12:45 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-10-07 13:55 [PATCHv4 0/3] pwm: imx: support output polarity inversion Lothar Waßmann
2014-10-07 13:55 ` Lothar Waßmann
2014-10-07 13:55 ` [PATCHv5 1/3] pwm: print error messages with pr_err() instead of pr_debug() Lothar Waßmann
2014-10-07 13:55   ` Lothar Waßmann
2014-10-07 13:55 ` [PATCHv5 2/3] pwm: make the PWM_POLARITY flag in DTB optional Lothar Waßmann
2014-10-07 13:55   ` Lothar Waßmann
2014-10-09 15:16   ` Thierry Reding
2014-10-09 15:16     ` Thierry Reding
2014-10-10 14:22     ` [PATCHv6 0/3] pwm: imx: support output polarity inversion Lothar Waßmann
2014-10-10 14:22       ` Lothar Waßmann
2014-10-10 14:22       ` [PATCHv6 1/3] pwm: print error messages with pr_err() instead of pr_debug() Lothar Waßmann
2014-10-10 14:22         ` Lothar Waßmann
2014-10-10 14:22       ` [PATCHv6 2/3] pwm: make the PWM_POLARITY flag in DTB optional Lothar Waßmann
2014-10-10 14:22         ` Lothar Waßmann
2014-10-10 14:22       ` [PATCH 3/3] pwm: imx: support output polarity inversion Lothar Waßmann
2014-10-10 14:22         ` Lothar Waßmann
2016-09-08 22:15       ` [PATCHv6 0/3] " Stefan Agner
2016-09-08 22:15         ` Stefan Agner
2016-09-09  7:18         ` Lothar Waßmann
2016-09-09  7:18           ` Lothar Waßmann
2016-09-12 12:45           ` Alexandre Belloni [this message]
2016-09-12 12:45             ` Alexandre Belloni
2016-09-12 14:04             ` Uwe Kleine-König
2016-09-12 14:04               ` Uwe Kleine-König
2016-09-12 16:51               ` Stefan Agner
2016-09-12 16:51                 ` Stefan Agner
2016-09-12 20:00                 ` Uwe Kleine-König
2016-09-12 20:00                   ` Uwe Kleine-König
2016-09-12 21:12                   ` Clemens Gruber
2016-09-12 21:12                     ` Clemens Gruber
2016-09-13  6:45                     ` Uwe Kleine-König
2016-09-13  6:45                       ` Uwe Kleine-König
2016-09-12 13:54           ` Vladimir Zapolskiy
2016-09-12 13:54             ` Vladimir Zapolskiy
2014-10-07 13:55 ` [PATCHv5 3/3] " Lothar Waßmann
2014-10-07 13:55   ` Lothar Waßmann

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