From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: [PATCH v2] pwm_backlight: Add device tree support for Low Threshold Brightness Date: Thu, 20 Sep 2012 23:16:45 -0600 Message-ID: <505BF83D.8040201@wwwdotorg.org> References: <1348203080-16348-1-git-send-email-avinashphilip@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1348203080-16348-1-git-send-email-avinashphilip@ti.com> Sender: linux-doc-owner@vger.kernel.org To: "Philip, Avinash" Cc: grant.likely@secretlab.ca, rob.herring@calxeda.com, rob@landley.net, rpurdie@rpsys.net, thierry.reding@avionic-design.de, broonie@opensource.wolfsonmicro.com, shawn.guo@linaro.org, devicetree-discuss@lists.ozlabs.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, nsekhar@ti.com, gururaja.hebbar@ti.com List-Id: devicetree@vger.kernel.org On 09/20/2012 10:51 PM, Philip, Avinash wrote: > Some backlights perform poorly when driven by a PWM with a short > duty-cycle. For such devices, the low threshold can be used to specify a > lower bound for the duty-cycle and should be chosen to exclude the > problematic range. > > This patch adds support for an optional low-threshold-brightness > property. > diff --git a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt > Optional properties: > - pwm-names: a list of names for the PWM devices specified in the > "pwms" property (see PWM binding[0]) > + - low-threshold-brightness: brightness threshold low level. Low threshold > + brightness set to value so that backlight present on low end of > + brightness. For my education, why not just specify values above this value in the brightness-levels array; how do those two interact? It seems like any description of that is missing from the PWM documentation, and would be good to have in the DT binding too.