From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752681AbcFVMBS (ORCPT ); Wed, 22 Jun 2016 08:01:18 -0400 Received: from nat-hk.nvidia.com ([203.18.50.4]:58246 "EHLO hkmmgate101.nvidia.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752646AbcFVMBN (ORCPT ); Wed, 22 Jun 2016 08:01:13 -0400 X-PGP-Universal: processed; by hkpgpgate102.nvidia.com on Wed, 22 Jun 2016 05:01:09 -0700 From: Laxman Dewangan To: , , , CC: , , , , Hyong Bin Kim , Laxman Dewangan Subject: [PATCH 3/5] pwm: tegra: fix overflow when calculating duty cycle Date: Wed, 22 Jun 2016 17:17:21 +0530 Message-ID: <1466596043-27262-4-git-send-email-ldewangan@nvidia.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1466596043-27262-1-git-send-email-ldewangan@nvidia.com> References: <1466596043-27262-1-git-send-email-ldewangan@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Hyong Bin Kim duty_ns * (1 << PWM_DUTY_WIDTH) could overflow in integer calcualtion when PWM rate is low. Hence do all calculation on unsigned long long to avoid overflow. Signed-off-by: Hyong Bin Kim Signed-off-by: Laxman Dewangan --- drivers/pwm/pwm-tegra.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/pwm/pwm-tegra.c b/drivers/pwm/pwm-tegra.c index 575ca8e..49cefd5 100644 --- a/drivers/pwm/pwm-tegra.c +++ b/drivers/pwm/pwm-tegra.c @@ -69,7 +69,7 @@ static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, int duty_ns, int period_ns) { struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip); - unsigned long long c; + unsigned long long c = duty_ns; unsigned long rate, hz; u32 val = 0; int err; @@ -79,7 +79,8 @@ static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, * per (1 << PWM_DUTY_WIDTH) cycles and make sure to round to the * nearest integer during division. */ - c = duty_ns * (1 << PWM_DUTY_WIDTH) + period_ns / 2; + c *= (1 << PWM_DUTY_WIDTH); + c += period_ns / 2; do_div(c, period_ns); val = (u32)c << PWM_DUTY_SHIFT; -- 2.1.4