From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751380Ab3LKKNZ (ORCPT ); Wed, 11 Dec 2013 05:13:25 -0500 Received: from [207.46.163.24] ([207.46.163.24]:38348 "EHLO co9outboundpool.messaging.microsoft.com" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751294Ab3LKKM4 (ORCPT ); Wed, 11 Dec 2013 05:12:56 -0500 X-Forefront-Antispam-Report: CIP:70.37.183.190;KIP:(null);UIP:(null);IPV:NLI;H:mail.freescale.net;RD:none;EFVD:NLI X-SpamScore: 0 X-BigFish: VS0(zzzz1f42h2148h208ch1ee6h1de0h1fdah2073h2146h1202h1e76h2189h1d1ah1d2ah1fc6hzzz2dh2a8h839he5bhf0ah1288h12a5h12a9h12bdh12e5h137ah139eh13b6h1441h1504h1537h162dh1631h1758h1898h18e1h1946h19b5h1ad9h1b0ah1b2fh2222h224fh1fb3h1d0ch1d2eh1d3fh1dc1h1dfeh1dffh1e23h1fe8h1ff5h2218h2216h226dh22d0h2327h2336h1155h) From: Xiubo Li To: , , , , Subject: [PATCH] leds: leds-pwm: fix duty time overflow. Date: Wed, 11 Dec 2013 17:19:42 +0800 Message-ID: <1386753582-16009-1-git-send-email-Li.Xiubo@freescale.com> X-Mailer: git-send-email 1.8.0 MIME-Version: 1.0 Content-Type: text/plain X-OriginatorOrg: freescale.com X-FOPE-CONNECTOR: Id%0$Dn%*$RO%0$TLS%0$FQDN%$TlsDn% X-FOPE-CONNECTOR: Id%0$Dn%FREESCALE.MAIL.ONMICROSOFT.COM$RO%1$TLS%0$FQDN%$TlsDn% Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Overflow maybe occurs when calculates the duty time. For instance, the period time is 990000000ns, and the max_brightness is 127, when setting the brightness to 12, the duty value will be 25906026ns, but it should be 93543307ns. --- drivers/leds/leds-pwm.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/leds/leds-pwm.c b/drivers/leds/leds-pwm.c index bb6f948..7cb2cd8 100644 --- a/drivers/leds/leds-pwm.c +++ b/drivers/leds/leds-pwm.c @@ -66,9 +66,11 @@ static void led_pwm_set(struct led_classdev *led_cdev, struct led_pwm_data *led_dat = container_of(led_cdev, struct led_pwm_data, cdev); unsigned int max = led_dat->cdev.max_brightness; - unsigned int period = led_dat->period; + unsigned long long duty = led_dat->period; - led_dat->duty = brightness * period / max; + duty *= brightness; + do_div(duty, max); + led_dat->duty = duty; if (led_dat->can_sleep) schedule_work(&led_dat->work); -- 1.8.4