Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753421AbZKNBMQ (ORCPT ); Fri, 13 Nov 2009 20:12:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752927AbZKNBMO (ORCPT ); Fri, 13 Nov 2009 20:12:14 -0500 Received: from mga01.intel.com ([192.55.52.88]:23862 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752861AbZKNBMN (ORCPT ); Fri, 13 Nov 2009 20:12:13 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.44,740,1249282800"; d="scan'208";a="513697373" Subject: RE: 2.6.31.4: WARNING: at arch/x86/kernel/hpet.c:390 hpet_next_event+0x70/0x80() [occurs when ACPI_PROCESSOR=y] From: "Pallipadi, Venkatesh" To: Justin Piszcz Cc: Thomas Gleixner , john stultz , lkml , Arjan van de Ven In-Reply-To: References: <20091111195016.GB22225@redhat.com> <1f1b08da0911121513l32d47b4x8b9722ad3440ceb6@mail.gmail.com> <1258069232.14894.9.camel@localhost.localdomain> <7E82351C108FA840AB1866AC776AEC467647ABBD@orsmsx505.amr.corp.intel.com> <1258137165.21141.20.camel@localhost.localdomain> Content-Type: text/plain Date: Fri, 13 Nov 2009 17:12:19 -0800 Message-Id: <1258161139.21141.29.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.24.3 (2.24.3-1.fc10) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2504 Lines: 72 On Fri, 2009-11-13 at 10:43 -0800, Justin Piszcz wrote: > > On Fri, 13 Nov 2009, Pallipadi, Venkatesh wrote: > > > On Fri, 2009-11-13 at 01:38 -0800, Thomas Gleixner wrote: > >> On Thu, 12 Nov 2009, Pallipadi, Venkatesh wrote: > >>> Yes. Yes. This is a hardware errata. I have a patch to workaround this and > >>> waiting on the errata description to get published.. > >> > >> Can we at least have some PCI quirk or whatever until you can push the > >> final workaround out so peoples machines do not explode ? > > > > Its a harmless bug functionality-wise and should not have any side > > effect other than triggering the WARN_ON_ONCE in hpet next event code. > > > > Thanks, > > Venki > > > > Venki, > > When the following patch is applied though: (courtesy of john stultz) > Justin, I am missing something in here. Without the below patch, on 2.6.31.4 and ACPI_PROCESSOR loaded (either as module or builtin), you may see the WARNING. But, that should not cause any other problems with C-states, P-states, or anything else. Is that what you are seeing? The below patch is not a workaround for the problem. Infact it will make situation worse with constant stream of prinkts and can reduce the C-state residency and turbo upside. Thanks, Venki > --- a/arch/x86/kernel/hpet.c > +++ b/arch/x86/kernel/hpet.c > @@ -376,7 +376,7 @@ static void hpet_set_mode(enum clock_event_mode mode, > static int hpet_next_event(unsigned long delta, > struct clock_event_device *evt, int timer) > { > - u32 cnt; > + u32 cnt, check; > > cnt = hpet_readl(HPET_COUNTER); > cnt += (u32) delta; > @@ -387,7 +387,12 @@ static int hpet_next_event(unsigned long delta, > * what we wrote hit the chip before we compare it to the > * counter. > */ > - WARN_ON_ONCE((u32)hpet_readl(HPET_Tn_CMP(timer)) != cnt); > + check = (u32)hpet_readl(HPET_Tn_CMP(timer)); > + if(check != cnt) { > + printk("hpet_next_event: hpet_writel failed: 0x%x != 0x%x\n", > + check, cnt); > + hpet_writel(cnt, HPET_Tn_CMP(timer)); > + } > > return (s32)((u32)hpet_readl(HPET_COUNTER) - cnt) >= 0 ? -ETIME : 0; > } > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/