From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752594Ab1GKJo2 (ORCPT ); Mon, 11 Jul 2011 05:44:28 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:33472 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752211Ab1GKJo1 (ORCPT ); Mon, 11 Jul 2011 05:44:27 -0400 Date: Mon, 11 Jul 2011 10:43:43 +0100 From: Catalin Marinas To: Russell King - ARM Linux Cc: Marc Zyngier , Vitaly Kuzmichev , "linux-arm-kernel@lists.infradead.org" , "linux-watchdog@vger.kernel.org" , Wim Van Sebroeck , "arm@kernel.org" , "linux-kernel@vger.kernel.org" , Arnd Bergmann , John Stultz , Nicolas Pitre , Thomas Gleixner Subject: Re: [PATCH V2 0/6] arm_smp_twd: mpcore_wdt: Fix MPCORE watchdog setup Message-ID: <20110711094343.GB11247@e102109-lin.cambridge.arm.com> References: <1286185540-19569-1-git-send-email-vkuzmichev@mvista.com> <1309892440-3260-1-git-send-email-vkuzmichev@mvista.com> <4E14337F.1050101@arm.com> <20110706101456.GN8286@n2100.arm.linux.org.uk> <20110706110548.GA31936@1n450.cable.virginmedia.net> <20110706111603.GS8286@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110706111603.GS8286@n2100.arm.linux.org.uk> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 06, 2011 at 12:16:03PM +0100, Russell King - ARM Linux wrote: > On Wed, Jul 06, 2011 at 12:05:48PM +0100, Catalin Marinas wrote: > > On Wed, Jul 06, 2011 at 11:14:56AM +0100, Russell King - ARM Linux wrote: > > > Do we know why the calibration was initially introduced? FWIR, it came > > > from the SMP group in ARM, so I guess they had a reason for it rather > > > than copying x86. > > > > I think it was introduced because the TWD frequency is half of the CPU > > frequency but the latter may not be known - boot monitor configuration > > could change it. > > Okay, that implies we can't have a fixed frequency built into the kernel > then. For such platforms like the ARM dev boards (realview + vexpress), > I expect we can read the CPU frequency from somewhere like one of the > ICST PLLs. That's highly platform dependent and it's not just ARM dev boards. Any board with ARM11MPCore, Cortex-A9 or Cortex-A5 would need to find a way to retrieve such information. If anyone is prepared to go through each board and figure out how to get the information, it's fine by me. -- Catalin