From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753927AbdLMCTo (ORCPT ); Tue, 12 Dec 2017 21:19:44 -0500 Received: from omzsmtpe02.verizonbusiness.com ([199.249.25.209]:32949 "EHLO omzsmtpe02.verizonbusiness.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753614AbdLMCAq (ORCPT ); Tue, 12 Dec 2017 21:00:46 -0500 From: alexander.levin@verizon.com Cc: Derek Basehore , Lee Jones , alexander.levin@verizon.com X-Host: surveyor.tdc.vzwcorp.com To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" Subject: [PATCH AUTOSEL for 4.4 41/59] backlight: pwm_bl: Fix overflow condition Thread-Topic: [PATCH AUTOSEL for 4.4 41/59] backlight: pwm_bl: Fix overflow condition Thread-Index: AQHTc7XjH/1A4+pbh0WDuk1f1NaLZw== Date: Wed, 13 Dec 2017 01:58:36 +0000 Message-ID: <20171213015817.6950-41-alexander.levin@verizon.com> References: <20171213015817.6950-1-alexander.levin@verizon.com> In-Reply-To: <20171213015817.6950-1-alexander.levin@verizon.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-messagesentrepresentingtype: 1 x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.144.60.250] Content-Type: text/plain; charset="iso-8859-1" MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id vBD2Jl9c017702 From: Derek Basehore [ Upstream commit 5d0c49acebc9488e37db95f1d4a55644e545ffe7 ] 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. Signed-off-by: Derek Basehore Acked-by: Thierry Reding Reviewed-by: Brian Norris Signed-off-by: Lee Jones Signed-off-by: Sasha Levin --- 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 ae3c6b6fd5db..d0c79153081d 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -79,14 +79,17 @@ 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) -- 2.11.0