From patchwork Thu Jul 22 14:52:27 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Daniel Thompson X-Patchwork-Id: 12394251 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5589AC63798 for ; Thu, 22 Jul 2021 14:53:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3862461278 for ; Thu, 22 Jul 2021 14:53:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232361AbhGVONJ (ORCPT ); Thu, 22 Jul 2021 10:13:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51584 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232571AbhGVONH (ORCPT ); Thu, 22 Jul 2021 10:13:07 -0400 Received: from mail-wm1-x329.google.com (mail-wm1-x329.google.com [IPv6:2a00:1450:4864:20::329]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B91AAC061799 for ; Thu, 22 Jul 2021 07:52:40 -0700 (PDT) Received: by mail-wm1-x329.google.com with SMTP id p9so1411340wmq.5 for ; Thu, 22 Jul 2021 07:52:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=NP0Nk6TpvGXmi3EQspzqhmeGXtJTWbb2t8lR/ui8TD4=; b=izUC5Qvf/tubSNdCEliUDdjaUor/iX8CATtMD/ErOTgRdDxMAKIFt3zG53ZHHOZogA xpLQ++qh4wvdPwv+BS2h+ZSz2nvLI+dJLauYxNCgRHa7dzFSLC7Du1yuHucHCt5Gnb4V ddRFrp71Lnb7AUlyWZ7QxMsJhrQTgPQGQO7NTG1h7M79yfis3wwcP2Hy0SraUA9F83lP M1Qv6MG5/oCL863uBERgRSzRsBaUPn2sqYNF7gw6CWT7f3uSr/sUOBtNU0H7REb5PqQT wtEbXtVjfTjbPDyvDi5uYllGTU1HAYEryx1rrTECSAXWMj0+0BWTbgPD6JvmCWqBEh7A UXJQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=NP0Nk6TpvGXmi3EQspzqhmeGXtJTWbb2t8lR/ui8TD4=; b=m1BxpVbogVdte3DHil7Oz+loKkqcQhTaPlPm9U7fE2FQtaFOkSokgtEkG++0MUcIjn /mohND/DZSEVdE3nO8cBwhHuF3oHWEOhQVEFLZUEgVO6lJHs7tDliyotTGZ8urnF43zE 09AsZoHr65Nle3s/hQfIAqVkaChcUdF2CWjBj/abbu3WS0kg+xG6g35Sr4EPFoY9nqPo 75RaEhtksTl7E3BdsBHfaboeMb3WAyFOQdjpEsy3rpzbXQbxrPit2tQS7bkSuoxhzugv LWzpQnjaDb41Ju3L7FYSq3nTnjfUGLnpLHulyKeNpe+z4x3TTC/5Lfd+TsX5vU2UNsrk Ey5w== X-Gm-Message-State: AOAM531PYcupS5pzuWHBQdQIIw8dBqhQ24Eh/srMLJ5LNyxTiQqO8Ygc G4u09MwK/ZT5xHO5oW6ND3gzIldSplgSBg== X-Google-Smtp-Source: ABdhPJy+uWxaydk70jwEcneHyghwzuOPld3QjaXdRC3fwtuprHx9eqlp5Y1QL6QB6ktCf4+LdElMcA== X-Received: by 2002:a05:600c:1c86:: with SMTP id k6mr43890478wms.147.1626965559165; Thu, 22 Jul 2021 07:52:39 -0700 (PDT) Received: from maple.lan (cpc141216-aztw34-2-0-cust174.18-1.cable.virginm.net. [80.7.220.175]) by smtp.gmail.com with ESMTPSA id t6sm30527687wru.75.2021.07.22.07.52.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Jul 2021 07:52:38 -0700 (PDT) From: Daniel Thompson To: Lee Jones , Jingoo Han Cc: Daniel Thompson , Thierry Reding , =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= , linux-pwm@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, Marek Vasut , stable@vger.kernel.org Subject: [PATCH v2] backlight: pwm_bl: Improve bootloader/kernel device handover Date: Thu, 22 Jul 2021 15:52:27 +0100 Message-Id: <20210722145227.1573115-1-daniel.thompson@linaro.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210722144623.1572816-1-daniel.thompson@linaro.org> References: <20210722144623.1572816-1-daniel.thompson@linaro.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org Currently there are (at least) two problems in the way pwm_bl starts managing the enable_gpio pin. Both occur when the backlight is initially off and the driver finds the pin not already in output mode and, as a result, unconditionally switches it to output-mode and asserts the signal. Problem 1: This could cause the backlight to flicker since, at this stage in driver initialisation, we have no idea what the PWM and regulator are doing (an unconfigured PWM could easily "rest" at 100% duty cycle). Problem 2: This will cause us not to correctly honour the post_pwm_on_delay (which also risks flickers). Fix this by moving the code to configure the GPIO output mode until after we have examines the handover state. That allows us to initialize enable_gpio to off if the backlight is currently off and on if the backlight is on. Reported-by: Marek Vasut Signed-off-by: Daniel Thompson Cc: stable@vger.kernel.org Fixes: 3698d7e7d221 ("backlight: pwm_bl: Avoid backlight flicker when probed from DT") Acked-by: Marek Vasut Tested-by: Marek Vasut --- Notes: v2: Added Fixes: tag (sorry for the noise) drivers/video/backlight/pwm_bl.c | 54 +++++++++++++++++--------------- 1 file changed, 28 insertions(+), 26 deletions(-) base-commit: 2734d6c1b1a089fb593ef6a23d4b70903526fe0c -- 2.30.2 diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index e48fded3e414..8d8959a70e44 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -409,6 +409,33 @@ static bool pwm_backlight_is_linear(struct platform_pwm_backlight_data *data) static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb) { struct device_node *node = pb->dev->of_node; + bool active = true; + + /* + * If the enable GPIO is present, observable (either as input + * or output) and off then the backlight is not currently active. + * */ + if (pb->enable_gpio && gpiod_get_value_cansleep(pb->enable_gpio) == 0) + active = false; + + if (!regulator_is_enabled(pb->power_supply)) + active = false; + + if (!pwm_is_enabled(pb->pwm)) + active = false; + + /* + * Synchronize the enable_gpio with the observed state of the + * hardware. + */ + if (pb->enable_gpio) + gpiod_direction_output(pb->enable_gpio, active); + + /* + * Do not change pb->enabled here! pb->enabled essentially + * tells us if we own one of the regulator's use counts and + * right now we do not. + */ /* Not booted with device tree or no phandle link to the node */ if (!node || !node->phandle) @@ -420,20 +447,7 @@ static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb) * assume that another driver will enable the backlight at the * appropriate time. Therefore, if it is disabled, keep it so. */ - - /* if the enable GPIO is disabled, do not enable the backlight */ - if (pb->enable_gpio && gpiod_get_value_cansleep(pb->enable_gpio) == 0) - return FB_BLANK_POWERDOWN; - - /* The regulator is disabled, do not enable the backlight */ - if (!regulator_is_enabled(pb->power_supply)) - return FB_BLANK_POWERDOWN; - - /* The PWM is disabled, keep it like this */ - if (!pwm_is_enabled(pb->pwm)) - return FB_BLANK_POWERDOWN; - - return FB_BLANK_UNBLANK; + return active ? FB_BLANK_UNBLANK: FB_BLANK_POWERDOWN; } static int pwm_backlight_probe(struct platform_device *pdev) @@ -486,18 +500,6 @@ static int pwm_backlight_probe(struct platform_device *pdev) goto err_alloc; } - /* - * If the GPIO is not known to be already configured as output, that - * is, if gpiod_get_direction returns either 1 or -EINVAL, change the - * direction to output and set the GPIO as active. - * Do not force the GPIO to active when it was already output as it - * could cause backlight flickering or we would enable the backlight too - * early. Leave the decision of the initial backlight state for later. - */ - if (pb->enable_gpio && - gpiod_get_direction(pb->enable_gpio) != 0) - gpiod_direction_output(pb->enable_gpio, 1); - pb->power_supply = devm_regulator_get(&pdev->dev, "power"); if (IS_ERR(pb->power_supply)) { ret = PTR_ERR(pb->power_supply);