From patchwork Fri Jun 12 16:26:17 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Philipp Zabel X-Patchwork-Id: 6599271 Return-Path: X-Original-To: patchwork-linux-fbdev@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 04E62C0020 for ; Fri, 12 Jun 2015 16:26:31 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 0F5E62066C for ; Fri, 12 Jun 2015 16:26:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C9CC32060E for ; Fri, 12 Jun 2015 16:26:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752713AbbFLQ02 (ORCPT ); Fri, 12 Jun 2015 12:26:28 -0400 Received: from metis.ext.pengutronix.de ([92.198.50.35]:60347 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750980AbbFLQ01 (ORCPT ); Fri, 12 Jun 2015 12:26:27 -0400 Received: from dude.hi.4.pengutronix.de ([10.1.0.7] helo=dude.pengutronix.de.) by metis.ext.pengutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1Z3Rmg-0007KD-NV; Fri, 12 Jun 2015 18:26:22 +0200 From: Philipp Zabel To: Thierry Reding Cc: Jingoo Han , Lee Jones , Ajay Kumar , linux-pwm@vger.kernel.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@pengutronix.de, Philipp Zabel Subject: [PATCH] pwm-backlight: Avoid backlight flicker when probed from DT Date: Fri, 12 Jun 2015 18:26:17 +0200 Message-Id: <1434126377-22545-1-git-send-email-p.zabel@pengutronix.de> X-Mailer: git-send-email 2.1.4 X-SA-Exim-Connect-IP: 10.1.0.7 X-SA-Exim-Mail-From: p.zabel@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-fbdev@vger.kernel.org Sender: linux-fbdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP If the driver is probed from the device tree, and there is a phandle property set on it, and the enable GPIO is already configured as output, and the backlight is currently disabled, keep it disabled. If all these conditions are met, assume there will be some other driver that can enable the backlight at the appropriate time. Signed-off-by: Philipp Zabel --- I have seen the thread at https://lkml.org/lkml/2014/7/31/259, but I'm not sure if it has come to a resolution. This is what I think could be useful to keep the current default behaviour of enabling the backlight while at the same time allowing to keep it disabled if we are absolutely certain that the backlight is currently off, and we think there is some other driver that will control it: --- drivers/video/backlight/pwm_bl.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index 6897f1c..dcb6bfb 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -199,6 +199,7 @@ static int pwm_backlight_probe(struct platform_device *pdev) struct backlight_properties props; struct backlight_device *bl; struct pwm_bl_data *pb; + int initial_blank = FB_BLANK_UNBLANK; int ret; if (!data) { @@ -263,8 +264,21 @@ static int pwm_backlight_probe(struct platform_device *pdev) pb->enable_gpio = gpio_to_desc(data->enable_gpio); } - if (pb->enable_gpio) - gpiod_direction_output(pb->enable_gpio, 1); + if (pb->enable_gpio) { + /* + * If the driver is probed from the device tree and there is a + * phandle link pointing to the backlight node, it is safe to + * assume that another driver will enable the backlight at the + * appropriate time. Therefore, if it is disabled, keep it so. + */ + if (of_find_property(pdev->dev.of_node, "phandle", NULL) && + gpiod_get_direction(pb->enable_gpio) == GPIOF_DIR_OUT && + gpiod_get_value(pb->enable_gpio) == 0) { + initial_blank = FB_BLANK_POWERDOWN; + } else { + gpiod_direction_output(pb->enable_gpio, 1); + } + } pb->power_supply = devm_regulator_get(&pdev->dev, "power"); if (IS_ERR(pb->power_supply)) { @@ -323,6 +337,7 @@ static int pwm_backlight_probe(struct platform_device *pdev) } bl->props.brightness = data->dft_brightness; + bl->props.power = initial_blank; backlight_update_status(bl); platform_set_drvdata(pdev, bl);