From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: cpufreq: powernow-k8 frequency transitions question Date: 02 Jan 2006 18:15:30 +0100 Message-ID: References: Mime-Version: 1.0 Return-path: In-Reply-To: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: cpufreq-bounces@lists.linux.org.uk Errors-To: cpufreq-bounces+glkc-cpufreq=m.gmane.org+glkc-cpufreq=m.gmane.org@lists.linux.org.uk Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Gunter Ohrner Cc: cpufreq@lists.linux.org.uk Gunter Ohrner writes: > I already asked this question on linux-kernel@vger.kernel.org but maybe this > list would be a more appropriate place... The proceedings of the Ottawa Linux Symposium 2004 (available online) have a detailed paper on the powernow-k8 driver. > I'm currently reading and playing with the powernow-k8 cpufreq driver > module. However so far I wasn't able to find out how frequency transitions > are dealt with that have to be made using intermediate steps, ie. > transitions which cannot be done in one single step. > > (I read about this at > http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/26094.PDF > p. 269f.) > > I found safety guards which return an error if an invalid frequency > transition ("lo-lo transition") is requested. Is this the only support for > these transitions currently implemented or did I miss something? > Is there more advanced support simply missing, or is the current behaviour > sufficient, and if yes, why does this suffice? > > How do the conservative/ondemand cpufreq governors cope with the kernel > advertising frequencies it cannot directly transition between? Step by step. The frequency/voltage transistion functions in powernow-k8.c go through them in loops. -Andi