From patchwork Tue Jun 7 10:13:49 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Lothar_Wa=C3=9Fmann?= X-Patchwork-Id: 631417 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3rP6qP293Hz9t3s for ; Tue, 7 Jun 2016 20:14:09 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754867AbcFGKOH (ORCPT ); Tue, 7 Jun 2016 06:14:07 -0400 Received: from mail.karo-electronics.de ([81.173.242.67]:65360 "EHLO mail.karo-electronics.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752727AbcFGKOF (ORCPT ); Tue, 7 Jun 2016 06:14:05 -0400 From: =?UTF-8?q?Lothar=20Wa=C3=9Fmann?= To: Jean-Christophe Plagniol-Villard , Jingoo Han , Lee Jones , Thierry Reding , Tomi Valkeinen , linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pwm@vger.kernel.org, Marcel Ziswiler , Ian Campbell , Kumar Gala , =?UTF-8?q?Lothar=20Wa=C3=9Fmann?= , Mark Rutland , Pawel Moll , Rob Herring , devicetree@vger.kernel.org Subject: [PATCHv2] backlight: pwm_bl: disable PWM when 'duty_cycle' is zero Date: Tue, 7 Jun 2016 12:13:49 +0200 Message-Id: <1465294429-8570-1-git-send-email-LW@KARO-electronics.de> X-Mailer: git-send-email 2.1.4 MIME-Version: 1.0 Sender: linux-pwm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pwm@vger.kernel.org '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 Acked-by: Rob Herring --- 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(-) diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt index 764db86..95fa8a9 100644 --- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt @@ -4,10 +4,13 @@ Required properties: - compatible: "pwm-backlight" - pwms: OF device-tree PWM specification (see PWM binding[0]) - brightness-levels: Array of distinct brightness levels. Typically these - are in the range from 0 to 255, but any range starting at 0 will do. + are in the range from 0 to 255, but any range will do. The actual brightness level (PWM duty cycle) will be interpolated - from these values. 0 means a 0% duty cycle (darkest/off), while the - last value in the array represents a 100% duty cycle (brightest). + from these values. 0 means a 0% duty cycle, while the highest value in + the array represents a 100% duty cycle. + The range may be in reverse order (starting with the maximum duty cycle + value) to create a PWM signal with the 100% duty cycle representing + minimum and 0% duty cycle maximum brigthness. - default-brightness-level: the default brightness level (index into the array defined by the "brightness-levels" property) - power-supply: regulator for supply voltage diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index b2b366b..80b2b52 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -103,8 +103,8 @@ static int pwm_backlight_update_status(struct backlight_device *bl) if (pb->notify) brightness = pb->notify(pb->dev, brightness); - if (brightness > 0) { - duty_cycle = compute_duty_cycle(pb, brightness); + duty_cycle = compute_duty_cycle(pb, brightness); + if (duty_cycle > 0) { pwm_config(pb->pwm, duty_cycle, pb->period); pwm_backlight_power_on(pb, brightness); } else