From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joel Fernandes Subject: Re: [PATCH 7/9] ARM: edma: Don't clear EMR of channel in edma_stop Date: Wed, 31 Jul 2013 20:59:27 -0500 Message-ID: <51F9C0FF.7030703@ti.com> References: <1375104595-16018-1-git-send-email-joelf@ti.com> <1375104595-16018-8-git-send-email-joelf@ti.com> <51F77982.7030601@ti.com> <51F89B0B.4080803@ti.com> <51F8DA5C.9060503@ti.com> Reply-To: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <51F8DA5C.9060503-l0cyMroinI0@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: Errors-To: davinci-linux-open-source-bounces-VycZQUHpC/PFrsHnngEfi1aTQe2KTcn/@public.gmane.org To: Sekhar Nori Cc: Mark Brown , Tony Lindgren , Grant Likely , Sricharan R , Russell King , Vinod Koul , Lokesh Vutla , Chris Ball , Arnd Bergmann , Rajendra Nayak , Rob Herring , Jason Kridner , Linux OMAP List , Linux ARM Kernel List , Linux DaVinci Kernel List , Balaji TK , Linux MMC List , Linux Kernel Mailing List , Santosh Shilimkar List-Id: linux-omap@vger.kernel.org On 07/31/2013 04:35 AM, Sekhar Nori wrote: > On Wednesday 31 July 2013 10:35 AM, Joel Fernandes wrote: >> On 07/30/2013 03:29 AM, Sekhar Nori wrote: >>> On Monday 29 July 2013 06:59 PM, Joel Fernandes wrote: >>>> We certainly don't want error conditions to be cleared anywhere >>> >>> 'anywhere' is a really loaded term. >>> >>>> as this will make us 'forget' about missed events. We depend on >>>> knowing which events were missed in order to be able to reissue them. >>> >>>> This fixes a race condition where the EMR was being cleared >>>> by the transfer completion interrupt handler. >>>> >>>> Basically, what was happening was: >>>> >>>> Missed event >>>> | >>>> | >>>> V >>>> SG1-SG2-SG3-Null >>>> \ >>>> \__TC Interrupt (Almost same time as ARM is executing >>>> TC interrupt handler, an event got missed and also forgotten >>>> by clearing the EMR). >>> >>> Sorry, but I dont see how edma_stop() is coming into picture in the race >>> you describe? >> >> In edma_callback function, for the case of DMA_COMPLETE (Transfer >> completion interrupt), edma_stop() is called when all sets have been >> processed. This had the effect of clearing the EMR. > > Ah, thanks. I was missing the fact that the race comes into picture only > when using the DMA engine driver. I guess that should be mentioned > somewhere since it is not immediately obvious. > > The patch looks good to me. So if you respin just this one with some > updated explanation based on what you wrote below, I will take it. Sure I'll do that. Also the trigger_channel patch, will you be taking that one too? I can send these 2 in a series as they touch arch/arm/common/edma.c Thanks, -Joel > > Thanks, > Sekhar > > -- > To unsubscribe from this list: send the line "unsubscribe linux-omap" in > the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >