From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759879Ab3BYKgO (ORCPT ); Mon, 25 Feb 2013 05:36:14 -0500 Received: from smtprelay03.ispgateway.de ([80.67.31.30]:42409 "EHLO smtprelay03.ispgateway.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759498Ab3BYKgN (ORCPT ); Mon, 25 Feb 2013 05:36:13 -0500 References: <20130222111521.GA25473@pd.tnic> <1361647210-12983-1-git-send-email-bp@alien8.de> <20130224112851.GA19609@pd.tnic> <20130224120952.GB19609@pd.tnic> <1361761600.2303.12.camel@rzhang1-mobl4> <20130225102049.GA12067@pd.tnic> Message-ID: X-Mailer: http://www.courier-mta.org/cone/ From: Peter Feuerer To: Borislav Petkov Cc: Zhang Rui , LKML , Durgadoss R , Borislav Petkov , Andreas Mohr , Alexander Lam Subject: Re: [PATCH] acerhdf: Fix fan activation with new thermal governor Date: Mon, 25 Feb 2013 11:36:04 +0100 Mime-Version: 1.0 Content-Type: text/plain; format=flowed; charset="US-ASCII" Content-Disposition: inline Content-Transfer-Encoding: 7bit X-Df-Sender: NDA0MDk0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, sorry for not answering to earlier mails, but sitting in front of the computer and writing English mails is still very exhausting for me. Borislav Petkov writes: > On Mon, Feb 25, 2013 at 11:06:40AM +0800, Zhang Rui wrote: >> when the temperature goes up to 50C, will the fan be turned on or not? > > Right, let's first clarify this: > > so we want the fan to go on when it reaches and/or exceeds the 'fanon' > temperature and to go off after it goes under the 'fanoff' temperature. > It is supposed to remain on in the [fanoff,fanon] interval. > > Now, my observation from yesterday was that, if we don't do the > flattening of the abovementioned interval in acerhdf_set_cur_state() but > we simply turn on the fan if we receive state=1 and turn it off when > state=0, the fan gets turned on only for short bursts when the governor > decides it is time to throttle, i.e. the temperature in the zone is > rising and turns it off when the temperature starts to fall again. And > it would turn on the fan at lower temperatures than fanon. > > But this is annoying. The main reason why this acerhdf thing was added > in the first place was to do a better fan control on those machines > because the fans are noisy. Basically, enable the fan only when really > needed - and leave it off when not because it is really annoying. > > When enabled, however, leave it on longer until a safe, 'fanoff' > temperature is reached. > > Am I making more sense now? Peter? This sounds good, couldn't have stated it more clear. Just one thing to add here: This is standard idea of a "schmitt trigger", we implemented in acerhdf :) http://en.wikipedia.org/wiki/Schmitt_trigger -- kind regards, --peter;