From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Renninger Subject: Re: [PATCH 2/8 v2] acpi-cpufreq: Add quirk to disable _PSD usage on all AMD CPUs Date: Mon, 17 Sep 2012 13:40:23 +0200 Message-ID: <201209171340.23801.trenn@suse.de> References: <1346747289-8421-1-git-send-email-andre.przywara@amd.com> <5056D420.80808@amd.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5056D420.80808@amd.com> Sender: cpufreq-owner@vger.kernel.org List-ID: Content-Type: Text/Plain; charset="us-ascii" To: Andre Przywara Cc: Konrad Rzeszutek Wilk , Andreas Herrmann , "Rafael J. Wysocki" , cpufreq@vger.kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Matthew Garret On Monday, September 17, 2012 09:41:20 AM Andre Przywara wrote: > On 09/15/2012 01:20 PM, Konrad Rzeszutek Wilk wrote: > > ... > This was to overcome some nasty interaction between the Windows > scheduler and their version of the ondemand governor. Whoever is/was responsible for this, can you explain him/her that this was a bad idea and why. Is this part of a BKDG? Can you point to a public spec and the exact wording of the "Windows scheduler workaround" BIOS vendors shall do? > + pr_info_once(PFX "overriding BIOS provided _PSD data\n"); The message shows up on nearly every platform wether a _PSD function exists or not. This is wrong. If it's _PSD info that should get ignored/overwritten, this should be done where _PSD is obtained: processor_perflib.c Are you sure that it will never make sense for AMD to make use of _PSD tables? If yes, then always ignoring might be an option. If not, this might need a more specific check, e.g.: - Latest Windows version support called via OSI interface? Latest Windowses should/may not need this anymore? - Check for Desktop CPUs that are affected by the bad spec? Hm, as powernow-k8 never made use of _PSD, ignoring it for now sounds like a good thing to do. Still the ignoring should get moved to processor_perflib.c, best with a pointer or at least a comment that _PSD can be dangerous on AMD platforms. At some day _PSD may make sense for AMD platforms as well? Thomas