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 12:23:47 +0200 Message-ID: <20130427102346.GA30588@amd.pavel.ucw.cz> References: <1366967993-3812-1-git-send-email-rui.zhang@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1366967993-3812-1-git-send-email-rui.zhang@intel.com> Sender: linux-kernel-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! > Commit 4ae46befb49d4173122e0afa995c4e93d01948a2 > introduces a regression that the fan is always on > even if the system is in idle state. > > My original idea in that commit is that: > when the current temperature is above the trip point, > keep the fan on, even if the temperature is dropping. > when the current temperature is below the trip point, > turn on the fan when the temperature is raising, > turn off the fan when the temperature is dropping. Is that even right algoritm? 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. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html