Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751998AbbFBTdb (ORCPT ); Tue, 2 Jun 2015 15:33:31 -0400 Received: from www.linutronix.de ([62.245.132.108]:52782 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750977AbbFBTdY (ORCPT ); Tue, 2 Jun 2015 15:33:24 -0400 Date: Tue, 2 Jun 2015 21:33:25 +0200 (CEST) From: Thomas Gleixner To: Adrian Hunter cc: LKML , Andy Lutomirski , Linus Torvalds , Andi Kleen , x86@kernel.org, "H. Peter Anvin" , Len Brown Subject: Re: [PATCH RFC] x86, tsc: Allow for high latency in quick_pit_calibrate() In-Reply-To: <1432194944-29087-1-git-send-email-adrian.hunter@intel.com> Message-ID: References: <1432194944-29087-1-git-send-email-adrian.hunter@intel.com> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 819 Lines: 24 On Thu, 21 May 2015, Adrian Hunter wrote: > If it takes longer than 12us to read the PIT counter lsb/msb, > then the error margin will never fall below 500ppm within 50ms, > and Fast TSC calibration will always fail. So finally the legacy PIT emulation takes longer than the 30 years old hardware implementation. Progress! > This patch detects when that will happen and switches to using > a slightly different algorithm that takes advantage of the PIT's > latch comand. Is there really no smarter way to figure out the TSC frequency on modern systems? Thanks, tglx -- 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/