From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Lutomirski Subject: Re: [PATCH v4 3/7] acpi-cpufreq: Add support for disabling dynamic overclocking Date: Sat, 23 Jul 2011 23:15:02 -0400 Message-ID: <4E2B8E36.6030308@mit.edu> References: <1311007062-2050-1-git-send-email-mjg@redhat.com> <1311007062-2050-4-git-send-email-mjg@redhat.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1311007062-2050-4-git-send-email-mjg@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Matthew Garrett Cc: cpufreq@vger.kernel.org, davej@redhat.com, linux-kernel@vger.kernel.org, borislav.petkov@amd.com, mark.langsdorf@amd.com, andreas.herrmann3@amd.com On 07/18/2011 12:37 PM, Matthew Garrett wrote: > One feature present in powernow-k8 that isn't present in acpi-cpufreq is > support for enabling or disabling AMD's core performance boost technology. > This patch adds that support to acpi-cpufreq, but also extends it to allow > Intel's dynamic acceleration to be disabled via the same interface. The > sysfs entry retains the cpb name for compatibility purposes. > > Signed-off-by: Matthew Garrett > --- > drivers/cpufreq/acpi-cpufreq.c | 191 ++++++++++++++++++++++++++++++++++++++++ > 1 files changed, 191 insertions(+), 0 deletions(-) > > + if (enable) > + reg->q&= ~MSR_IA32_MISC_ENABLE_TURBO_DISABLE; > + else > + reg->q |= MSR_IA32_MISC_ENABLE_TURBO_DISABLE; > + } I was curious and looked it up. Intel SDM volume 3, 14.3.2.1 says: Opportunistic processor performance operation can be disabled by setting bit 38 of IA32_MISC_ENABLE. This mechanism is intended for BIOS only. If IA32_MISC_ENABLE[38] is set, CPUID.06H:EAX[1] will return 0. and the next section says: System software can temporarily disengage opportunistic processor performance operation by setting bit 32 of the IA32_PERF_CTL MSR (0199H), using a read- modify-write sequence on the MSR. Would that be a better way to control boost mode on Intel chips? --Andy