From patchwork Mon Jun 24 20:31:13 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthias Kaehlcke X-Patchwork-Id: 11014081 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 4837014BB for ; Mon, 24 Jun 2019 20:31:32 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3894F28B90 for ; Mon, 24 Jun 2019 20:31:32 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2C8FA28BBE; Mon, 24 Jun 2019 20:31:32 +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 CDA7128B90 for ; Mon, 24 Jun 2019 20:31:31 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 5411689DC7; Mon, 24 Jun 2019 20:31:29 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mail-pl1-x641.google.com (mail-pl1-x641.google.com [IPv6:2607:f8b0:4864:20::641]) by gabe.freedesktop.org (Postfix) with ESMTPS id 76C5F89DC2 for ; Mon, 24 Jun 2019 20:31:26 +0000 (UTC) Received: by mail-pl1-x641.google.com with SMTP id bi6so7534206plb.12 for ; Mon, 24 Jun 2019 13:31:26 -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=uZKHvCx8L/nRTrUb/ohywx0d3IXX3vcHyiOoGdIF2Vg=; b=NUDgWWxxf4nvayWGVWhtq8ePv6VQ2RCC/FtdllCYiuFJfe0yVRB+8Evc3LfIoOyans VCHVGIsfffBLVCU9xKySMtWlA1I7huAcglFRFnTXJvq1PZ8T1aL8tib2HD4EjBfpTJ1+ 1AuHxRgvweEhjTW9IUd4OnKr4Mrg6FJ/fE/ZDty9caQ5sh/yULjGn5yCzqzfG7hV9qvW kxwGhqDALRCJP1SoGMA5iYdJJJ+PoOXzSIfJGmrT6dAToNhkPgtAROPN6x1R1KA1uAEH O3ytSR6EQux3BbiC/efaUb1916XHXhL8MygAY7ZOxddnXa9KKzbyhv7gPt4ByA/xDzti VmSw== X-Gm-Message-State: APjAAAXNal2q5vPF5KfIj0UahyqXOq8CbGAMYdo/1VaGWNiA0CKC/ei8 dnAid6kAIXsfCwatKxRXP+qDVQ== X-Google-Smtp-Source: APXvYqzY0+srP89wCVDbPca+cx8EHxAJHQuHwUe5lX3IaE2YnttbyJ+9Ii8mxU7OnlFea1FBJZ1y0Q== X-Received: by 2002:a17:902:2006:: with SMTP id n6mr94261265pla.232.1561408286127; Mon, 24 Jun 2019 13:31:26 -0700 (PDT) Received: from localhost ([2620:15c:202:1:75a:3f6e:21d:9374]) by smtp.gmail.com with ESMTPSA id r2sm21887470pfl.67.2019.06.24.13.31.25 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 24 Jun 2019 13:31:25 -0700 (PDT) From: Matthias Kaehlcke To: Thierry Reding , Lee Jones , Daniel Thompson , Jingoo Han , Bartlomiej Zolnierkiewicz Subject: [PATCH v2 4/4] backlight: pwm_bl: Set scale type for brightness curves specified in the DT Date: Mon, 24 Jun 2019 13:31:13 -0700 Message-Id: <20190624203114.93277-5-mka@chromium.org> X-Mailer: git-send-email 2.22.0.410.gd8fdbe21b5-goog In-Reply-To: <20190624203114.93277-1-mka@chromium.org> References: <20190624203114.93277-1-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=uZKHvCx8L/nRTrUb/ohywx0d3IXX3vcHyiOoGdIF2Vg=; b=G/bUhQslRBb9yDeN/Ju1v2H78Jn3pcV6lvi6ZsyGVCuBbzJ+oIhAcvU04QfS10U/4R pdE3J6hWbwxyP4QcHwwtH00UNcd1LgYEz2XOvY5wmOr4tiTSrA/9uD0OATvj9bqrmoPn id+vaY8rgFoQ9n7vUdhFL4XPoNNii/WHKNs9A= 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 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 f067fe7aa35d..2297fb4af49d 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