From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9C24CC3279B for ; Wed, 4 Jul 2018 08:44:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5558A2408F for ; Wed, 4 Jul 2018 08:44:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linaro.org header.i=@linaro.org header.b="d36K3RgB" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5558A2408F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934451AbeGDIni (ORCPT ); Wed, 4 Jul 2018 04:43:38 -0400 Received: from mail-wr0-f195.google.com ([209.85.128.195]:40863 "EHLO mail-wr0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933050AbeGDIl2 (ORCPT ); Wed, 4 Jul 2018 04:41:28 -0400 Received: by mail-wr0-f195.google.com with SMTP id t6-v6so4450720wrn.7 for ; Wed, 04 Jul 2018 01:41:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=SY0bY6e63LD/+pmaO/g2UMIUwsVRUSxVO3M4oq7KIVg=; b=d36K3RgBzvK/Cck64Ai6f3/XK85re9ruDhAezF4wgObdyKZRhctXrJxBzRBviFURNk cxGtdaNQSGaOgoHTON7uZnNB06laQlNkqQHcSAoB94KSXntnU0p/SsAsRMNgGqLNNGp7 0sCP1ceX9gqNNbfGD2eXFcnOBKr8LX0uwjAco= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=SY0bY6e63LD/+pmaO/g2UMIUwsVRUSxVO3M4oq7KIVg=; b=MYVj2P5PHxqchipR+GXQWrR+nk4sH0WEEnnmwxE330IsX4jkw4I6zy4iZp0Z3UYOJd Jpp1ddBCWcpq9peZ9lagItGjNalRofwP94Hs5KKbLjTT4crJHI2vsHpVtn3L/rb2VXVp OwMqlWja75kO2u0DhOxsUYuGEXEBwVZrfO6fkufNcVziYY/4DzZ+ERr+fl0oHPZ4Kf+R MzwKw6cH1Yt3sMm6a0dn2fbnJb/l02+3B/9mlZyU7eFUugRACC+ousa5yq5QEAG15SPK Z9/tVr+FMVAPQ9EZvdu1DVcW4q8/l4gjk1wOFVvgHIC1DIoDI9qGu74ZqV4OGqfiwFqh ki+Q== X-Gm-Message-State: APt69E2F1LhuxJ63iqoRkpx+B0TzPzvjoQVdZhQMJxJjjv1s/nSdgZYg Z5YxgZCCYOH+mmbckbDkSlYFBmUab6g= X-Google-Smtp-Source: AAOMgpcbymgZKhpkHy64M5Ofp/bkHuqVKsw+7YmTwBR5bspwUcYjf0rYC1PZXdMYGXlaNKLz/FeCXw== X-Received: by 2002:a5d:46c6:: with SMTP id g6-v6mr847435wrs.76.1530693686884; Wed, 04 Jul 2018 01:41:26 -0700 (PDT) Received: from [192.168.8.101] ([37.173.73.209]) by smtp.googlemail.com with ESMTPSA id r140-v6sm5931206wmd.27.2018.07.04.01.41.25 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 04 Jul 2018 01:41:25 -0700 (PDT) Subject: Re: [PATCH 0/2] Allwinner A64 timer workaround To: Samuel Holland , Marc Zyngier , Maxime Ripard , Chen-Yu Tsai , Catalin Marinas , Will Deacon , Thomas Gleixner Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-sunxi@googlegroups.com, Mark Rutland References: <20180511022751.9096-1-samuel@sholland.org> <2c16d5ab-38f7-8f3e-875c-19e8032f440a@arm.com> From: Daniel Lezcano Message-ID: <439ea6ab-9834-64d5-2aff-1a4ac7e3890d@linaro.org> Date: Wed, 4 Jul 2018 10:41:28 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/07/2018 20:42, Samuel Holland wrote: > On 07/03/18 10:09, Marc Zyngier wrote: >> On 11/05/18 03:27, Samuel Holland wrote: >>> Hello, >>> >>> Several people (including me) have experienced extremely large system >>> clock jumps on their A64-based devices, apparently due to the architectural >>> timer going backward, which is interpreted by Linux as the timer wrapping >>> around after 2^56 cycles. >>> >>> Investigation led to discovery of some obvious problems with this SoC's >>> architectural timer, and this patch series introduces what I believe is >>> the simplest workaround. More details are in the commit message for patch >>> 1. Patch 2 simply enables the workaround in the device tree. >> >> What's the deal with this series? There was a couple of nits to address, and >> I was more or less expecting a v2. > > I got reports that people were still occasionally having clock jumps after > applying this series, so I wanted to attempt a more complete fix, but I haven't > had time to do any deeper investigation. I think this series is still beneficial > even if it's not a complete solution, so I'll come back with another patch on > top of this if/once I get it fully fixed. > > I'll prepare a v2 with a bounded loop. Presumably, 3 * (max CPU Hz) / (24MHz > timer) ≈ 150 should be a conservative iteration limit? > > Also, does this make sense to CC to stable? I understand a partial fix is better than nothing but if you can narrow down the issue and provide patches to fix it in one shot that would be awesome. -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog