From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: [PATCH] ACPI thermal: do not always return THERMAL_TREND_RAISING for active trip points Date: Sat, 27 Apr 2013 20:38:00 +0200 Message-ID: <20130427183800.GA8929@amd.pavel.ucw.cz> References: <1366967993-3812-1-git-send-email-rui.zhang@intel.com> <20130427102346.GA30588@amd.pavel.ucw.cz> <1367065950.2128.11.camel@rzhang1-mobl4> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1367065950.2128.11.camel@rzhang1-mobl4> Sender: linux-acpi-owner@vger.kernel.org To: Zhang Rui Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-acpi@vger.kernel.org, rjw@sisk.pl, lenb@kernel.org, eduardo.valentin@ti.com List-Id: linux-pm@vger.kernel.org Hi! > > Is that even right algoritm? > > > sorry the changelog is not clear enough here. > I should say, > "keep the fan on when the temperature is raising" > "turn off the fan when the temperature is dropping" > > > Assume I'm running at very cold room, lets say -10C. Assume idle CPU > > will hover around 30C with no fan, or hover around 10C with fan > > running, trip point being 50C. > > > > You _could_ leave fan off until 50C, having silent, passively cooled > > system. > > > > What it will do instead is annoyingly pulse fan at 10C. > > > First, fan will never spins on if the temperature never hits 50C. > > let's see how ACPI 3.0 fan (just have on and off state) is supposed to > work after overheat. > 1. temperature goes above 50C > 2. Fan starts to spin. > 3. a) if temperature goes higher (if possible), fan keeps on. > b) if temperature drops, but still above 50C. the fan keeps on. > c) if temperature drops below 50C, the last temperature is above 50C, > thus the fan is turned off. > d) if the temperature goes higher again, the fan will not spin on > until the temperature is higher than the trip point (50C) again. So the fan is spinning iff the temperature is over threshold, right? > is this behavior what you want? That's better, yes. Even better would be if it had some hysteresis: turn the fan on at threshold temperature, but turn it off only if it drops below temperature-5C, or if it is below threshold for 1 minute. Thanks, Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html