From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Renninger Subject: Re: [PATCH v2] acpi: Fix regression where _PPC is not read at boot even when ignore_ppc=0 Date: Thu, 16 Apr 2009 12:01:11 +0200 Message-ID: <200904161201.13409.trenn@suse.de> References: <20090415225348.GW8311@plum> <20090416002712.GX8311@plum> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from cantor.suse.de ([195.135.220.2]:56377 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754737AbZDPKBR (ORCPT ); Thu, 16 Apr 2009 06:01:17 -0400 In-Reply-To: <20090416002712.GX8311@plum> Content-Disposition: inline Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: djwong@us.ibm.com Cc: linux-kernel , Ingo Molnar , cpufreq@vger.kernel.org, linux-acpi@vger.kernel.org Hi, be careful, this could break the T60 again. Can you and Ingo place acpidump of your machines somewhere, please. On Thursday 16 April 2009 02:27:12 Darrick J. Wong wrote: > Earlier, Ingo Molnar posted a patch to make it so that the kernel would avoid > reading _PPC on his broken T60. Unfortunately, it seems that with Thomas > Renninger's patch last July to eliminate _PPC evaluations when the processor > driver loads, the kernel never actually reads _PPC at all! This is wrong. _PPC is only evaluated when a cpufreq driver got registered. > This is problematic > if you happen to boot your non-T60 computer in a state where the BIOS _wants_ > _PPC to be something other than zero. Your machine should suffer from that since Ingo's T60 patch? Reading the _PPC part of the ACPI spec again: --- In order to support dynamic changes of _PPC object, Notify events on the processor object. Notify events of type 0x80 will cause OSPM to reevaluate any _PPC objects residing under the particular processor object notified. --- The *reevaluate* implies that the _PPC value has been evaluated/initialized by the OS already and Ingo's patch would be wrong then. I'd like to have a look at the T60's ACPI parts and find out what exactly (or if at all) makes _PPC to return sane values, I expect it's _PDC. Hmm, I could also imagine that Ingo's T60 patch is not needed anymore since Yakui's patch (0ac3c571315a53c14d2733564f14ebdb911fe903). This one could make sure that _PDC is evaluated first making the internal ACPI _PPC state initialize and makes sure _PPC gets only called afterwards. If this patch does not break Ingo's T60, I think this should go in. Due to Yakui's reordering/cleanup of ACPI function calls, I think also the notifier chain I introduced is not needed anymore and I can clean this up if I find some time. > So, put the _PPC evaluation back into acpi_processor_get_performance_info if > ignore_ppc isn't 1. > > This second version restores the correct function call, which simplifies > the patch. I apologize for the churn and the poor eyesight. > > Signed-off-by: Darrick J. Wong > --- > > drivers/acpi/processor_perflib.c | 6 +++++- > 1 files changed, 5 insertions(+), 1 deletions(-) > > > diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c > index cafb410..85af717 100644 > --- a/drivers/acpi/processor_perflib.c > +++ b/drivers/acpi/processor_perflib.c > @@ -348,7 +348,11 @@ static int acpi_processor_get_performance_info(struct acpi_processor *pr) > if (result) > goto update_bios; > > - return 0; > + /* We need to call _PPC once when cpufreq starts */ > + if (ignore_ppc != 1) > + result = acpi_processor_get_platform_limit(pr); > + > + return result; > > /* > * Having _PPC but missing frequencies (_PSS, _PCT) is a very good hint that You are more or less reverting Ingo's patch (e4233dec749a3519069d9390561b5636a75c7579): diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c index 5207f9e..cbb6f08 100644 --- a/drivers/acpi/processor_perflib.c +++ b/drivers/acpi/processor_perflib.c @@ -322,10 +322,6 @@ static int acpi_processor_get_performance_info(struct acpi_processor *pr) if (result) return result; - result = acpi_processor_get_platform_limit(pr); - if (result) - return result; - return 0; } Thomas