Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757291Ab0KLMxc (ORCPT ); Fri, 12 Nov 2010 07:53:32 -0500 Received: from mailgw10.se.ericsson.net ([193.180.251.61]:54498 "EHLO mailgw10.se.ericsson.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754778Ab0KLMxb convert rfc822-to-8bit (ORCPT ); Fri, 12 Nov 2010 07:53:31 -0500 X-AuditID: c1b4fb3d-b7b28ae00000135b-e0-4cdd38c93635 From: Harald Gustafsson To: Linus Walleij , Colin Cross CC: "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , Russell King , srinidhi kasagar , Varun Swara , Catalin Marinas , Rickard ANDERSSON Date: Fri, 12 Nov 2010 13:49:50 +0100 Subject: RE: [PATCH] [ARM] twd: Allow twd rescaling to match cpu frequency Thread-Topic: [PATCH] [ARM] twd: Allow twd rescaling to match cpu frequency Thread-Index: AcuCZrd7inK6IVsuQW+DFluTgJX8+gAAWC9G Message-ID: References: <1283396674-4865-1-git-send-email-ccross@android.com>, In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1961 Lines: 53 Hi, Don't forget the other patches to make this work: [ARM] twd: Always calibrate local timer [ARM] twd: Fix updating control register in set_mode [ARM] twd: Fix prescaler getting cleared by set_mode /Harald Gustafsson ________________________________________ From: Linus Walleij [linus.ml.walleij@gmail.com] Sent: Friday, November 12, 2010 1:39 PM To: Colin Cross Cc: linux-kernel@vger.kernel.org; linux-arm-kernel@lists.infradead.org; Russell King; srinidhi kasagar; Varun Swara; Catalin Marinas; Harald Gustafsson; Rickard ANDERSSON Subject: Re: [PATCH] [ARM] twd: Allow twd rescaling to match cpu frequency Hi Colin, 2010/9/2 Colin Cross : > The clock to the ARM TWD local timer scales with the cpu > frequency. To allow the cpu frequency to change while > maintaining a constant TWD frequency, pick a lower target > frequency for the TWD and use the prescaler to divide down > to the closest lower frequency. > > This patch provides a new initialization function that takes > a target TWD frequency and the relation between the cpu > clock and the TWD clock, required to be an integer divider >>= 2 by the ARM spec. It also provides a function to be > called from cpufreq drivers to set the prescaler whenever > the cpu frequency changes. What's the status of this patch? We have basically the same problem so we'd really like a generic solution to this problem. Our only comment is that we cannot see the reason for not using the CPUfreq notifiers as most scaling code is, but I assume there is some specific reason for this? Unless something holds this back, could you post it to Russells patch tracker, we might have an add-on patch for the U8500 later. Yours, Linus Walleij -- 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/