From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Sender: rtc-linux@googlegroups.com Received: from mailout3.samsung.com (mailout3.samsung.com. [203.254.224.33]) by gmr-mx.google.com with ESMTPS id po17si341833pab.2.2016.07.05.01.52.31 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 05 Jul 2016 01:52:31 -0700 (PDT) Received: from epcpsbgr2.samsung.com (u142.gpu120.samsung.co.kr [203.254.230.142]) by mailout3.samsung.com (Oracle Communications Messaging Server 7.0.5.31.0 64bit (built May 5 2014)) with ESMTP id <0O9U01ZAI3BH7V00@mailout3.samsung.com> for rtc-linux@googlegroups.com; Tue, 05 Jul 2016 17:52:29 +0900 (KST) Message-id: <577B7537.4080506@samsung.com> Date: Tue, 05 Jul 2016 14:22:07 +0530 From: Alim Akhtar MIME-version: 1.0 To: Krzysztof Kozlowski , rtc-linux@googlegroups.com, linux-kernel@vger.kernel.org Cc: alexandre.belloni@free-electrons.com, javier@osg.samsung.com, pankaj.dubey@samsung.com Subject: [rtc-linux] Re: [RFC PATCH 2/2] rtc: s3c: Add s3c_rtc_{enable/disable}_clk in s3c_rtc_setfreq() References: <1467630195-6929-1-git-send-email-alim.akhtar@samsung.com> <1467630195-6929-2-git-send-email-alim.akhtar@samsung.com> <577B6CD9.80605@samsung.com> In-reply-to: <577B6CD9.80605@samsung.com> Content-type: text/plain; charset=UTF-8; format=flowed Reply-To: rtc-linux@googlegroups.com List-ID: List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , On 07/05/2016 01:46 PM, Krzysztof Kozlowski wrote: > On 07/04/2016 01:03 PM, Alim Akhtar wrote: >> As per code flow it is possible that s3c_rtc_setfreq() might get called >> with rtc clock disabled and in set_freq we perform h/w registers read/write, >> which might results in a kernel crash while probing rtc driver. >> Below is one such case: >> s3c_rtc_probe() >> clk_prepare_enable(info->rtc_clk) // rtc clock enabled >> s3c_rtc_gettime() // will enable clk if not done, and disable it upon exit >> s3c_rtc_setfreq() //then this will be called with clk disabled > > The indentation suggests levels of calls (chain) not sequence. This > should be: > s3c_rtc_probe() > clk_prepare_enable(info->rtc_clk) // rtc clock enabled > s3c_rtc_gettime() // will enable clk if not done, and disable it upon exit > s3c_rtc_setfreq() //then this will be called with clk disabled > >> >> This patch take cares of such issue by adding s3c_rtc_{enable/disable}_clk in >> s3c_rtc_setfreq(). > > What I don't get is that you wrote "it is *possible* that > s3c_rtc_setfreq() *might* get called". From my understanding this will > happen always because src_rtc_gettime() always disables the clocks. > > Why it does not happen always? > Yes, you are right, it is always disabled when reaches s3c_rtc_setfreq(). And I observed a kernel crash while testing on exynos7 platform in s3c_rtc_setfreq() because clock was always disabled at this point. And this patches fixes this issue. > Best regards, > Krzysztof > -- You received this message because you are subscribed to "rtc-linux". Membership options at http://groups.google.com/group/rtc-linux . Please read http://groups.google.com/group/rtc-linux/web/checklist before submitting a driver. --- You received this message because you are subscribed to the Google Groups "rtc-linux" group. To unsubscribe from this group and stop receiving emails from it, send an email to rtc-linux+unsubscribe@googlegroups.com. For more options, visit https://groups.google.com/d/optout.