From mboxrd@z Thu Jan 1 00:00:00 1970 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=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 B1D37C3A5A6 for ; Thu, 19 Sep 2019 14:06:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 85FC0214AF for ; Thu, 19 Sep 2019 14:06:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=rasmusvillemoes.dk header.i=@rasmusvillemoes.dk header.b="W4FhrPJA" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389771AbfISOGo (ORCPT ); Thu, 19 Sep 2019 10:06:44 -0400 Received: from mail-lj1-f195.google.com ([209.85.208.195]:38021 "EHLO mail-lj1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389045AbfISOGd (ORCPT ); Thu, 19 Sep 2019 10:06:33 -0400 Received: by mail-lj1-f195.google.com with SMTP id y23so3741619ljn.5 for ; Thu, 19 Sep 2019 07:06:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rasmusvillemoes.dk; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=k4SJ+eSfjSAP63ushly3GU0Efl4ebkKBMuWTSOkSqS8=; b=W4FhrPJAR9Dqgs5qFA5Pl22WVgeXGbokdSlE6Xjl8ev+AwkvtlovQkmnKhocbnMFdS 81B7iYoNdsvMs2yQlsvxAdJGvvAKDR0FvjYPLiSIbpwUt9AMKu8kvddB2vIg68Gs3TZA XspHxRzEPQhGFNCyXRy2eUNIWhGekZOWx5Sfw= 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=k4SJ+eSfjSAP63ushly3GU0Efl4ebkKBMuWTSOkSqS8=; b=UHoorSYByjIita2OBCwiWOUg1/EV/pcp5K9SxLYz835jVIQkW1n6CdyjyuVjU3cArI JFSihOr2QT/tVwXtH6L/9Sw8Wyx3fik7mHFYxwcU3gjntGDdzIMCxtyLwwhOrFuTA+UF Kl64DVLVgJS0rQCnaAJU3fn0hKb11XJXEKh1Htf1p+IdcAWxgXo4pL0SErfsPl30+bmD B7NZi8y8FQzd/W+7q2mZLOKhWqcLwMOVD0emttr1kOJn/XOGXDY6jrTW9iv20BCZH/Cp 9Hq+5PKlOqiVdSQjM8sO3+nkyCNuxAN9erWqGyZLVtK5R+uI0QqCtjZv+MY3ttk6wy7F tCDQ== X-Gm-Message-State: APjAAAXG2faME0rdGWv5fkO01QP4WpvL4D6/xmfJf/iyQ9uS4PdVqwIf OF/XswcdlkRQZ+ofQJKKA4l9Lg== X-Google-Smtp-Source: APXvYqzlHJRhLqL82K2xKbtjAXAMpinhzWwpvMBA7qVfJ7tNQ26aw9X0BviaTA3hpMKKf3q8cAewtQ== X-Received: by 2002:a2e:934f:: with SMTP id m15mr5586940ljh.101.1568901991526; Thu, 19 Sep 2019 07:06:31 -0700 (PDT) Received: from prevas-ravi.prevas.se ([81.216.59.226]) by smtp.gmail.com with ESMTPSA id h3sm1687886ljf.12.2019.09.19.07.06.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Sep 2019 07:06:31 -0700 (PDT) From: Rasmus Villemoes To: Thierry Reding , Lee Jones , Daniel Thompson , Jingoo Han , Bartlomiej Zolnierkiewicz Cc: Rasmus Villemoes , linux-pwm@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 3/5] backlight: pwm_bl: drop use of int_pow() Date: Thu, 19 Sep 2019 16:06:18 +0200 Message-Id: <20190919140620.32407-3-linux@rasmusvillemoes.dk> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190919140620.32407-1-linux@rasmusvillemoes.dk> References: <20190919140620.32407-1-linux@rasmusvillemoes.dk> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The scheduler uses a (currently private) fixed_power_int() in its load average computation for computing powers of numbers 0 < x < 1 expressed as fixed-point numbers, which is also what we want here. But that requires the scale to be a power-of-2. We could (and a following patch will) change to use a power-of-2 scale, but for a fixed small exponent of 3, there's no advantage in using repeated squaring. Signed-off-by: Rasmus Villemoes --- drivers/video/backlight/pwm_bl.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index 9252d51f31b9..aee6839e024a 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -179,7 +179,8 @@ static u64 cie1931(unsigned int lightness, unsigned int scale) if (lightness <= (8 * scale)) { retval = DIV_ROUND_CLOSEST(lightness * 10, 9033); } else { - retval = int_pow((lightness + (16 * scale)) / 116, 3); + retval = (lightness + (16 * scale)) / 116; + retval *= retval * retval; retval = DIV_ROUND_CLOSEST_ULL(retval, (scale * scale)); } -- 2.20.1