From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kukjin Kim Subject: RE: [PATCH] arm: mct: Don't reset the counter during boot and resume Date: Wed, 04 Jun 2014 10:47:22 +0900 Message-ID: <026701cf7f96$ed616a00$c8243e00$@samsung.com> References: <1401821299-24431-1-git-send-email-chirantan@chromium.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: Received: from mailout3.samsung.com ([203.254.224.33]:34570 "EHLO mailout3.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752036AbaFDBrZ (ORCPT ); Tue, 3 Jun 2014 21:47:25 -0400 Received: from epcpsbgr3.samsung.com (u143.gpu120.samsung.co.kr [203.254.230.143]) by mailout3.samsung.com (Oracle Communications Messaging Server 7u4-24.01 (7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTP id <0N6M00CSIFMY1ZA0@mailout3.samsung.com> for linux-samsung-soc@vger.kernel.org; Wed, 04 Jun 2014 10:47:22 +0900 (KST) In-reply-to: Content-language: ko Sender: linux-samsung-soc-owner@vger.kernel.org List-Id: linux-samsung-soc@vger.kernel.org To: 'Doug Anderson' , 'Chirantan Ekbote' Cc: 'Russell King' , 'Olof Johansson' , 'Tomasz Figa' , linux-arm-kernel@lists.infradead.org, 'linux-samsung-soc' Doug Anderson wrote: > > Chirantan, > > On Tue, Jun 3, 2014 at 11:48 AM, Chirantan Ekbote > wrote: > > Unfortunately on some exynos systems, resetting the mct counter also > > resets the architected timer counter. This can cause problems if the > > architected timer driver has already been initialized because the kernel > > will think that the counter has wrapped around, causing a big jump in > > printk timestamps and delaying any scheduled clock events until the > > counter reaches the value it had before it was reset. > > > > The kernel code makes no assumptions about the initial value of the mct > > counter so there is no reason from a software perspective to clear the > > counter before starting it. This also fixes the problems described in > > the previous paragraph. > > > > Cc: Olof Johansson > > Cc: Doug Anderson > > Cc: Kukjin Kim > > Cc: Tomasz Figa > > Cc: linux-arm-kernel@lists.infradead.org > > Cc: linux-samsung-soc@vger.kernel.org > > Signed-off-by: Chirantan Ekbote > > --- > > drivers/clocksource/exynos_mct.c | 9 +++------ > > 1 file changed, 3 insertions(+), 6 deletions(-) > > I can confirm that this fixes problems I described in > . Now > when I boot there's no mysterious delay and there's no big jump in > time. > > I'd love to see this in 3.16 so we can get rid of this annoying delay. > > Reviewed-by: Doug Anderson > Tested-by: Doug Anderson OK, I will queue this patch into fixes for 3.16. Thanks, Kukjin