From patchwork Tue Aug 29 20:40:02 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "dbasehore ." X-Patchwork-Id: 807292 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-pwm-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=chromium.org header.i=@chromium.org header.b="Di2n1d+z"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3xhgVv5zHBz9s9Y for ; Wed, 30 Aug 2017 06:40:07 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751263AbdH2UkH (ORCPT ); Tue, 29 Aug 2017 16:40:07 -0400 Received: from mail-pf0-f179.google.com ([209.85.192.179]:34327 "EHLO mail-pf0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750909AbdH2UkG (ORCPT ); Tue, 29 Aug 2017 16:40:06 -0400 Received: by mail-pf0-f179.google.com with SMTP id l87so3555121pfj.1 for ; Tue, 29 Aug 2017 13:40:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id; bh=q/ueOxF+k/1dzzjCf5iQwWGuTGQK2DxIgpbLeCQntk8=; b=Di2n1d+zQ8ZLEqiIVPh8D/ZT2iENq7BQGZ2jjatIp18RkVxJaQfkn9SPOwNkjhiS/0 iLFJQIVXkdfPPp15bMWQd1AJYDY6uRXA1oBuwTfzj5ZnyDksAYAMY9kGiAesulCwnlv1 T/sObyBiOjG+iZhje39SOTBwSU7K5fvkqLKYE= 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; bh=q/ueOxF+k/1dzzjCf5iQwWGuTGQK2DxIgpbLeCQntk8=; b=HqFdBOmhERt9dZNIi3wMECGOf96BRDlWUyTUbDcs+EQ7jBoyixntzb/P66PLQDeJox egTOVQeGNssd6u3tbU4SG0MjC45vGIx0FPbDK9MXETh8VxT/VlsnajY5gYOdDwD2V/aC hvwpIikPUMzbSUC7PfoJxUAm3w53bbOBrDFEnYyCKtVsn2SDne818219qR2YCZXqc78k JAr/KZyHkDWSiHkTxeslaWFf38H1o7XHMTYwXLfB1j7GkUrH0dPIKkJGrZKZV1cuymtf Z8Rc4PGNFwXYIHEXKRiRMQEaBnYq93VNC+D9oVFXVu8GucyGk0baw9ErLNKdysRIDLkd dGsA== X-Gm-Message-State: AHYfb5gJtMChc9buwn3ygIj/ZcSQwZvd/onaVb/E2qF/N2g9T3xERISK jjKUciZ+jtVtnw/L X-Received: by 10.99.38.65 with SMTP id m62mr1536495pgm.226.1504039206072; Tue, 29 Aug 2017 13:40:06 -0700 (PDT) Received: from exogeni.mtv.corp.google.com ([2620:0:1000:1600:211e:5908:95bc:4888]) by smtp.gmail.com with ESMTPSA id g20sm5960883pfg.138.2017.08.29.13.40.04 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 29 Aug 2017 13:40:05 -0700 (PDT) From: Derek Basehore To: linux-kernel@vger.kernel.org Cc: thierry.reding@gmail.com, jingoohan1@gmail.com, lee.jones@linaro.org, briannorris@chromium.org, linux-pwm@vger.kernel.org, Derek Basehore Subject: [PATCH v2] pwm_bl: Fix overflow condition Date: Tue, 29 Aug 2017 13:40:02 -0700 Message-Id: <20170829204002.8663-1-dbasehore@chromium.org> X-Mailer: git-send-email 2.14.1.342.g6490525c54-goog Sender: linux-pwm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pwm@vger.kernel.org This fixes an overflow condition that can happen with high max brightness and period values in compute_duty_cycle. This fixes it by using a 64 bit variable for computing the duty cycle. Change-Id: I745c67c7a24740316d13eaf1be74248ea2249353 Signed-off-by: Derek Basehore --- drivers/video/backlight/pwm_bl.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index 76311ec5e400..5ccc8e34b7a6 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -88,14 +88,17 @@ static void pwm_backlight_power_off(struct pwm_bl_data *pb) static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness) { unsigned int lth = pb->lth_brightness; - int duty_cycle; + u64 duty_cycle; if (pb->levels) duty_cycle = pb->levels[brightness]; else duty_cycle = brightness; - return (duty_cycle * (pb->period - lth) / pb->scale) + lth; + duty_cycle *= pb->period - lth; + do_div(duty_cycle, pb->scale); + + return duty_cycle + lth; } static int pwm_backlight_update_status(struct backlight_device *bl)