From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arjan van de Ven Subject: Re: [PATCH v2 3/6] PowerCap: Added to drivers build Date: Mon, 07 Oct 2013 08:46:26 -0700 Message-ID: <5252D752.90401@linux.intel.com> References: <1380904616-17519-1-git-send-email-srinivas.pandruvada@linux.intel.com> <201310041917.01126.gheskett@wdtv.com> <525186B2.1000205@linux.intel.com> <201310061616.00303.gheskett@wdtv.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1256; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mga01.intel.com ([192.55.52.88]:56135 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755376Ab3JGPrR (ORCPT ); Mon, 7 Oct 2013 11:47:17 -0400 In-Reply-To: <201310061616.00303.gheskett@wdtv.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Gene Heskett Cc: Srinivas Pandruvada , "Brown, Len" , Jacob Pan , Linux PM list , Linux Kernel , Greg KH , "Rafael J. Wysocki" On 10/6/2013 1:15 PM, Gene Heskett wrote: >> and if you wonder what linux does today without the framework; there are >> mechanisms that kick in at the very end of the range, that are very >> draconian like taking the 3.0Ghz processor down to effectively 100MHz, >> or even a system reboot. The point of what Jacob and Srinivas are trying >> to add is to intervene slightly earlier (these failsafe mechanisms are >> still there) but much much more gently. > > First off, we are not using the type of boards for controllers that would > burn anything up sans its normal cooling, which is entirely passive on an > atom powered board as you well know. So there is no fan to fail and start > your doomsday scenario in abut 30% of the cases now, but there are a rather > dukes mixture of other boards being used yet. Those will be replaced in > due time as they fail, or the IRQ latency finally starts costing the shop > owner money because the machine can't be run at the optimum speed with that > poorly architect-ed board, probably with Atoms or BBB's. so if your system today never hits the thermal shutdown... ... you're not going to hit anything powercapping either. > If you insist on doing this, in the face of ample evidence its nothing but > a feel good action on your part, then the least we ask is for a tally > signal output, far enough in advance, say 0.25 seconds, to do a graceful, btw one thing to note that this is just the kernel mechanism; the actual knobs that it provides get turned by some userspace daemon.. I would fully expect that if you even ship such a daemon on your realtime device, that you build in the notification for sure. > In fact, I'd go so far as to say that any hardware capable of self- > destructing in normal operation, does not need to guarded by this proposed > function, but blacklisted instead, it is patently a defective design from > square one regardless of the brand name on the box. Or just let it burn > up, the warranty returns will educate the maker/designer soon enough. self-destruct or reboot... either case you will not like it.