From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bruno Ducrot Subject: Re: writing a cpufreq driver Date: Fri, 22 Sep 2006 17:44:48 +0200 Message-ID: <20060922154448.GO4945@poupinou.org> References: <20060921193141.GE17065@redhat.com> <1449F58C868D8D4E9C72945771150BDF153669@SAUSEXMB1.amd.com> <20060921194714.GH17065@redhat.com> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <20060921194714.GH17065@redhat.com> 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=gmane.org+glkc-cpufreq=gmane.org@lists.linux.org.uk Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Dave Jones Cc: Cpufreq@lists.linux.org.uk, nemesis@icequake.net On Thu, Sep 21, 2006 at 03:47:14PM -0400, Dave Jones wrote: > On Thu, Sep 21, 2006 at 02:38:22PM -0500, Langsdorf, Mark wrote: > > > > 1. The first time cpufreq changes speed, I get the whole > > > "Losing some > > > > ticks... checking if CPU frequency changed." then > > > eventually "Losing too > > > > many ticks!" and timer switches to PIT. This does not > > > happen when I use > > > > the /dev/toshiba driver to change speeds from userspace. > > > Not sure what > > > > is going on here... SMI handler latency is between 6 and 7 ms. > > > > > > Is loops_per_jiffy being correctly scaled on a speed transition? > > > Hmm, powernow-k7.c seems to be the only driver that's calling > > > recalibrate_cpu_khz() > > > > Do drivers need to be doing that? I would have thought the > > time could would do it after receiving the notification. > > Looking at it again.. > cpufreq_notify_transition() is calling adjust_jiffies() > which should be doing the same thing, so we should be good to go. > > It looks like feasible that recalibrate_cpu_khz() could actually > be killed off. It's called only at init time because cpu_khz is not reliable on some platform due to braindamaged BIOS that switch frequency of the K7 onto the SMM handler when ACPI enable performance control, breaking AMD recommandation at the same time BTW. -- Bruno Ducrot -- Which is worse: ignorance or apathy? -- Don't know. Don't care.