linux-kernel - Re: [PATCHv2] backlight: pwm_bl: disable PWM when 'duty

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Message-ID: <20160608200643.GA13510@rob-hp-laptop>
Date:	Wed, 8 Jun 2016 15:06:43 -0500
From:	Rob Herring <robh@...nel.org>
To:	Lothar Waßmann <LW@...O-electronics.de>
Cc:	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Jingoo Han <jingoohan1@...il.com>,
	Lee Jones <lee.jones@...aro.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pwm@...r.kernel.org,
	Marcel Ziswiler <marcel.ziswiler@...adex.com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Mark Rutland <mark.rutland@....com>,
	Pawel Moll <pawel.moll@....com>, devicetree@...r.kernel.org
Subject: Re: [PATCHv2] backlight: pwm_bl: disable PWM when 'duty_cycle' is
 zero

On Tue, Jun 07, 2016 at 12:13:49PM +0200, Lothar Waßmann wrote:
> 'brightness' is usually an index into a table of duty_cycle values,
> where the value at index 0 may well be non-zero
> (tegra30-apalis-eval.dts and tegra30-colibri-eval-v3.dts are real-life
> examples).
> Thus brightness == 0 does not necessarily mean that the PWM output
> will be inactive.
> Check for 'duty_cycle == 0' rather than 'brightness == 0' to decide
> whether to disable the PWM.
> 
> Signed-off-by: Lothar Waßmann <LW@...O-electronics.de>
> ---
> Changes wrt. v1:
>   - update binding docs to reflect the change
> 
>  .../devicetree/bindings/leds/backlight/pwm-backlight.txt         | 9 ++++++---
>  drivers/video/backlight/pwm_bl.c                                 | 4 ++--
>  2 files changed, 8 insertions(+), 5 deletions(-)

Acked-by: Rob Herring <robh@...nel.org>