From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Sender: rtc-linux@googlegroups.com Received: from mailout1.w1.samsung.com (mailout1.w1.samsung.com. [210.118.77.11]) by gmr-mx.google.com with ESMTPS id i135si324919pfe.0.2016.07.05.01.16.30 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 05 Jul 2016 01:16:31 -0700 (PDT) Received: from eucpsbgm2.samsung.com (unknown [203.254.199.245]) by mailout1.w1.samsung.com (Oracle Communications Messaging Server 7.0.5.31.0 64bit (built May 5 2014)) with ESMTP id <0O9U009E41NFGL50@mailout1.w1.samsung.com> for rtc-linux@googlegroups.com; Tue, 05 Jul 2016 09:16:27 +0100 (BST) Subject: [rtc-linux] Re: [RFC PATCH 2/2] rtc: s3c: Add s3c_rtc_{enable/disable}_clk in s3c_rtc_setfreq() To: Alim Akhtar , rtc-linux@googlegroups.com, linux-kernel@vger.kernel.org References: <1467630195-6929-1-git-send-email-alim.akhtar@samsung.com> <1467630195-6929-2-git-send-email-alim.akhtar@samsung.com> Cc: alexandre.belloni@free-electrons.com, javier@osg.samsung.com, pankaj.dubey@samsung.com From: Krzysztof Kozlowski Message-id: <577B6CD9.80605@samsung.com> Date: Tue, 05 Jul 2016 10:16:25 +0200 MIME-version: 1.0 In-reply-to: <1467630195-6929-2-git-send-email-alim.akhtar@samsung.com> Content-type: text/plain; charset=UTF-8 Reply-To: rtc-linux@googlegroups.com List-ID: List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , 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? 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.