From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752427AbaJBVNn (ORCPT ); Thu, 2 Oct 2014 17:13:43 -0400 Received: from mail-qa0-f54.google.com ([209.85.216.54]:48104 "EHLO mail-qa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751282AbaJBVNm (ORCPT ); Thu, 2 Oct 2014 17:13:42 -0400 Date: Thu, 2 Oct 2014 17:13:31 -0400 From: Eduardo Valentin To: Lukasz Majewski Cc: Zhang Rui , Linux PM list , Lukasz Majewski , Bartlomiej Zolnierkiewicz , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] thermal: step_wise: fix: Prevent from binary overflow when trend is dropping Message-ID: <20141002211325.GA5016@developer> References: <1411547232-21493-1-git-send-email-l.majewski@samsung.com> <1411547232-21493-2-git-send-email-l.majewski@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1411547232-21493-2-git-send-email-l.majewski@samsung.com> User-Agent: Mutt/1.5.22 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Lukasz, On Wed, Sep 24, 2014 at 10:27:10AM +0200, Lukasz Majewski wrote: > It turns out that some boards can have instance->lower greater than 0 and > when thermal trend is dropping it results with next_target equal to -1. > > Since the next_target is defined as unsigned long it is interpreted as > 0xFFFFFFFF and larger than instance->upper. > As a result the next_target is set to instance->upper which ramps up to > maximal cooling device target when the temperature is steadily decreasing. > Thanks for finding a problem and sending a fix. Can you please explain a little more on how next_target reaches -1 when lower is greater than 0? > Signed-off-by: Lukasz Majewski > --- > drivers/thermal/step_wise.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/thermal/step_wise.c b/drivers/thermal/step_wise.c > index 3b54c2c..fdd1f52 100644 > --- a/drivers/thermal/step_wise.c > +++ b/drivers/thermal/step_wise.c > @@ -77,7 +77,7 @@ static unsigned long get_target_state(struct thermal_instance *instance, > next_target = instance->upper; > break; > case THERMAL_TREND_DROPPING: > - if (cur_state == instance->lower) { > + if (cur_state <= instance->lower) { > if (!throttle) > next_target = THERMAL_NO_TARGET; > } else { > -- > 2.0.0.rc2 > Eduardo