From patchwork Tue Jul 9 19:00:07 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthias Kaehlcke X-Patchwork-Id: 11037411 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A84B8912 for ; Tue, 9 Jul 2019 19:00:24 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 98A1C2870D for ; Tue, 9 Jul 2019 19:00:24 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8CF332872F; Tue, 9 Jul 2019 19:00:24 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 3AAB22870D for ; Tue, 9 Jul 2019 19:00:24 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 5BE8C6E09C; Tue, 9 Jul 2019 19:00:22 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mail-pl1-x643.google.com (mail-pl1-x643.google.com [IPv6:2607:f8b0:4864:20::643]) by gabe.freedesktop.org (Postfix) with ESMTPS id 4F3CB6E094 for ; Tue, 9 Jul 2019 19:00:19 +0000 (UTC) Received: by mail-pl1-x643.google.com with SMTP id a93so10566391pla.7 for ; Tue, 09 Jul 2019 12:00:19 -0700 (PDT) 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=7VTnoQhILwKHLps+gGfkisxkuSKBxEyo68mEBQUHAaY=; b=M9IaHS2PzQujHKp0gHfRU95R4i068TVh4UhlKzM0EzVfnQ984AjGuKNBNmxCdonWne B6HF3Pbty91FxWtmGtBC7f9c8QbiaOabiW1SPTkDn0DANgPqeq15F9zwnCBOL1voISkG XsiSMuPH0LKCcKVxsY8kVweexAXn8pXS4q6EcftGz6G9eaCIfEPgLqOHQSZR5q3Q1+dy /ldBgNjz53stg1eP/0TjBSGVE9FSneaMGu8W/PzXYN4skz6U8xcdSaYWoiQ1dgc3ivvb 5G1HCDfw9pLEYaeEPywGC67TdV3PRGd2gJg/2Q9bmRpGzeckxDIIiPnz8FXn2mI3KVyP Dvhw== X-Gm-Message-State: APjAAAWtVlifvXM/pzNqqt6DO4YXx4I9eVBpY9Ma9O/AgdIFHis49j+B KGTFjgpNAYcx+8z5V63tNMOH+w== X-Google-Smtp-Source: APXvYqyFxcn+t9rWGoWrMrwk7IGCCiVhSunnF0u4fJQLec9Z7/8us2QIzzEsGo2V3Ixk/lZr9QooRQ== X-Received: by 2002:a17:902:29e6:: with SMTP id h93mr32447140plb.297.1562698818959; Tue, 09 Jul 2019 12:00:18 -0700 (PDT) Received: from localhost ([2620:15c:202:1:75a:3f6e:21d:9374]) by smtp.gmail.com with ESMTPSA id v63sm8391683pfv.174.2019.07.09.12.00.18 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 09 Jul 2019 12:00:18 -0700 (PDT) From: Matthias Kaehlcke To: Thierry Reding , Lee Jones , Daniel Thompson , Jingoo Han , Bartlomiej Zolnierkiewicz Subject: [PATCH v3 4/4] backlight: pwm_bl: Set scale type for brightness curves specified in the DT Date: Tue, 9 Jul 2019 12:00:07 -0700 Message-Id: <20190709190007.91260-5-mka@chromium.org> X-Mailer: git-send-email 2.22.0.410.gd8fdbe21b5-goog In-Reply-To: <20190709190007.91260-1-mka@chromium.org> References: <20190709190007.91260-1-mka@chromium.org> MIME-Version: 1.0 X-Mailman-Original-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=7VTnoQhILwKHLps+gGfkisxkuSKBxEyo68mEBQUHAaY=; b=kfV/7/kvbkaJ7UsIzdsFDRlAMdzpK6L6mf+hCSJgo/ppqnLdG493pA1TwsgBo8gqI+ 4m8IhLpUYafypQV62VutcuQ/xBvf5+Qfw9xSrUk4r15c6IIY+l2X2T26Z72GsIoqOOBe J11qlTxGksNKv6aSrfL+fr+Nca1CmutGbOxRA= X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-pwm@vger.kernel.org, linux-fbdev@vger.kernel.org, Brian Norris , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Douglas Anderson , Matthias Kaehlcke , Jacek Anaszewski , Pavel Machek , Enric Balletbo i Serra Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Virus-Scanned: ClamAV using ClamSMTP Check if a brightness curve specified in the device tree is linear or not and set the corresponding property accordingly. This makes the scale type available to userspace via the 'scale' sysfs attribute. To determine if a curve is linear it is compared to a interpolated linear curve between min and max brightness. The curve is considered linear if no value deviates more than +/-5% of ${brightness_range} from their interpolated value. Signed-off-by: Matthias Kaehlcke Acked-by: Daniel Thompson --- Changes in v3: - none Changes in v2: - use 128 (power of two) instead of 100 as factor for the slope - add comment about max quantization error - added Daniel's 'Acked-by' tag --- drivers/video/backlight/pwm_bl.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index 7c6dfc4a601d..fef98beb8b7e 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -404,6 +404,31 @@ int pwm_backlight_brightness_default(struct device *dev, } #endif +static bool pwm_backlight_is_linear(struct platform_pwm_backlight_data *data) +{ + unsigned int nlevels = data->max_brightness + 1; + unsigned int min_val = data->levels[0]; + unsigned int max_val = data->levels[nlevels - 1]; + /* + * Multiplying by 128 means that even in pathological cases such + * as (max_val - min_val) == nlevels the error at max_val is less + * than 1%. + */ + unsigned int slope = (128 * (max_val - min_val)) / nlevels; + unsigned int margin = (max_val - min_val) / 20; /* 5% */ + int i; + + for (i = 1; i < nlevels; i++) { + unsigned int linear_value = min_val + ((i * slope) / 128); + unsigned int delta = abs(linear_value - data->levels[i]); + + if (delta > margin) + return false; + } + + return true; +} + static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb) { struct device_node *node = pb->dev->of_node; @@ -567,6 +592,11 @@ static int pwm_backlight_probe(struct platform_device *pdev) pb->levels = data->levels; } + + if (pwm_backlight_is_linear(data)) + props.scale = BACKLIGHT_SCALE_LINEAR; + else + props.scale = BACKLIGHT_SCALE_NON_LINEAR; } else if (!data->max_brightness) { /* * If no brightness levels are provided and max_brightness is