From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Langsdorf Subject: Using out of band messages to change min/max frequencies Date: Wed, 14 Mar 2012 12:36:28 -0500 Message-ID: <4F60D71C.6070709@calxeda.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: Sender: cpufreq-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: "cpufreq@vger.kernel.org" Does cpufreq currently support having an out-of-band agent change the available minimum/maximum frequency and then have the current frequency conform to the new values? I experimented with a notifier routine (from an IPC context) that used cpufreq_get_policy() and cpufreq_update_policy(). I ran into two problems: 1) cpufreq_update_policy() would overwrite the changes I made to the minimum/maximum settings 2) the driver->target call would be called within the notifier context, and would explode when it called its own notifiers. driver->bios_limit doesn't seem like the right answer, since it wouldn't be called if the current governor has a static policy (ie performance, powersave). Is there some better way to approach this? Ideally, I'd like something like the ACPI _PPC concept, but looking over that code I'm not sure it actually limits the frequency correctly. --Mark Langsdorf Calxeda, Inc.